PHP userland backwards compatibility layer that emulates PHP 5.5+ core functions.

⌈⌋ ⎇ branch:  upgrade.php


Artifact [7edd489be3]

Artifact 7edd489be337c809e79260b9c1619b078485dc99:

  • File ext/contrib/pdo_mysql.php — part of check-in [1bd07841f1] at 2014-04-24 02:22:36 on branch trunk — (no comment) (user: mario size: 42399)

<?php
/**
 * api: php
 * title: Procedural pdo_* interface mimicking mysql_* functions
 * version: 0.9.3
 * priority: EXPERIMENTAL
 * license: Public Domain
 * type: functions
 * suggests: upgradephp
 * config:  <const name="PDO_HELPFUL" type="select" value="0=None|1=Notice|2=Syntax" help="Provide additional notices for common pitfalls"/>   <const name="PDO_SEEKABLE" type="int" value="0" help="Adds a faux cursor wrapper atop PDOStatement to allow seeking across result rows. Set to 1 to enable, or any larger integer for caching rows."/>
 * category: library
 * url: http://fossil.include-once.org/upgradephp/finfo?name=ext/contrib/pdo_mysql.php
 * requires: php (>= 5.1.3), php:pdo
 * doc: http://stackoverflow.com/a/20767765
 *
 *
 * The dated mysql_* functions are chaperoned by deprecation nagging and cursorily
 * mentions of PDO and MSQLI. Forced-switching APIs is kinda pointless however when
 * bound parameters go unmentioned and code rewriting remains prohibitive.
 *
 * This collection of functions provide pdo_ lookalikes for most mysql_* functions.
 * Rewriting is as simple as changing to:
 *
 *   pdo_connect       <-  mysql_connect
 *   pdo_query         <-  mysql_query
 *   pdo_result        <-  mysql_result
 *   pdo_fetch_array   <-  mysql_fetch_array
 *   pdo_escape_string <-  mysql_real_escape_string
 *
 * With the addition of an extended pdo_query() interface the cumbersome SQL
 * concatenation and easily forgotten escaping are obsolete:
 *
 *   mysql_query("SELECT whatever FROM tbl WHERE id='$id' OR x=$x");
 *                                                      \       \
 * Becomes:                                               \      \
 *                                                          \     \
 *   pdo_query("SELECT whatever FROM tbl WHERE id=? OR x=?", $id, $x);
 *                                                \      \--------/
 *                                                 \---------/
 *
 * It's as simple as moving interpolated variables from the query into separate
 * parameters, and leaving plain question mark ? placeholders (without quotes)
 * in the SQL.
 * Just keep track of a matching value-to-placeholder order.
 *
 * For variables separated out that way, any previous ***_real_escape_string
 * applying becomes redundant. (Though the long-winded escaping+intermingling
 * approach was still possible if you'd unreasonably prefer).
 * Get rid of or fix any oldschool sanitize() function once you have converted
 * every innovocation to bound parameters.
 *
 *
 * Caveats and tips
 *
 *   HANDLES    pdo_query() and pdo_connect() return objects instead of
 *     resource handles. Commonly used plain boolean if() result tests may
 *     remain. But replace any is_resource() checks with is_object().
 *
 *   FREEING    You neither need pdo_close() or pdo_free_result() anymore.
 *     Just unset the result handles, it's all cleaned up automatically.
 *
 *   SEEKING    The old mysql extension was a memory hog. It did buffer all
 *     result data, so could seek back and forth. For PDO results it's best
 *     to just iterate over them only once. Consider using a foreach()
 *     preferrably.
 *     If you need arbitrary  pdo_result(), _fetch_lengths(), _data_seek()
 *     access, please enable PDO_SEEKABLE. It does refetch if need be for
 *     out-of-order retrieval. (Mysqld itself provides enough buffering.)
 *
 *   BOUND PARAMETERS    In SQL only values can be bound parameters with ?
 *     placeholders. Identifiers like table names, column names can't. You
 *     still have to use interpolation (with withelisting) for those.
 *     Likewise can't LIMIT ?,? clauses be used in pdo_query(). Use
 *     typecasted interpolated numbers there.
 *
 *   NAMED PARAMETERS    Besides ? placeholders there are also :named_keys.
 *     pdo_query() supports those too if passed as a single array with
 *     :key => value pairs.  You can only use either or.
 *
 *   SOMETHING DOESN'T WORK    Before asking for personal support anywhere
 *     on the Internet, please have the courtesy to `print pdo_error();`
 *     first. Always enable `error_reporting(E_ALL);` and `display_errors`
 *     and keep the `PDO_HELPFUL` constant enabled while developing.
 *
 *   GLOBAL OBJECT   The pdo_ wrappers keep the default connection in the
 *     global $pdo variable. Whose name is unlikely to clash with existing
 *     code, but potentially compatible with recent as by-product.
 *
 *
 * Rewriting advise
 *
 *   HYBRID    You can mix the old-style function use with PDO-esque
 *     accessing of result sets. For example
 *
 *         pdo_query("SELECT *")->fetchAll()
 *
 *     Packs all results into one list of row arrays.
 *     Which is also significantly shorter than:
 *
 *         while ($row = pdo_fetch_assoc($result)) {
 *            $array[] = $row;
 *         }
 *
 *     But PDO even allows to directly loop over the $result object.
 *
 *         foreach (pdo_query("SELECT * FROM tbl") as $assoc) {}
 *
 *     Currently doesn't work for PDOStatement_Seekable wrapped results.
 *
 *   TRANSITION   Likewise can you access PDO itself from the global handle,
 *     if you want to progressively switch to the native interface:
 *
 *         $pdo->prepare("INSERT INTO log VALUES (?)")->execute(array($msg));
 *
 *     You can still mix in pdo_query() and other function wrappers, if you
 *     utilize the $pdo variable from the shared scope, or pass it as $link
 *     parameter.
 *
 *
 *
 *
 *
 *
 */




// provide development tips (deprecated and redundant functions), set to 2 for SQL syntax warnings about unbound strings
defined("PDO_HELPFUL") or
define("PDO_HELPFUL", 1);


// apply PDO wrapper for random-access row seeking / faux cursor
defined("PDO_SEEKABLE") or
define("PDO_SEEKABLE", 1);  // set this to a higher integer (e.g. 500) to enable a cache for random access


// upgradephp
defined("E_USER_DEPRECATED") or
define("E_USER_DEPRECATED", E_USER_NOTICE);




// define functions just once
if (!function_exists("pdo_query")) {




  /**
   * Return the number of rows affected by last query.
   *
   */
  function pdo_affected_rows($stmt=NULL) {
     return pdo_stmt($stmt)->rowCount();
  }




  /**
   * What mysql thinks the charset of strings in PHP to be.
   *
   */
  function pdo_client_encoding($link=NULL) {
     return pdo_query("SELECT @@character_set_client AS cs", pdo_handle($link))->fetchObject()->cs;
  }
  



  /**
   * Disconnect by removing $pdo object.
   *
   */  
  function pdo_close($link=NULL) {
     PDO_HELPFUL and pdo_trigger_error("pdo_close() Does not need to be called usually. Just unset() your database handle.", E_USER_DEPRECATED);

     if ($link) {
        unset($link);
     }
     else {
        $GLOBALS["pdo"] = /*unset with*/ new pdo_dummy("No database connection. You had just disconnected using pdo_close()!");
     }
  }




  /**
   * Connect to database.
   *
   * Also stores the newest PDO handle in the global `$pdo` variable.
   *
   */  
  function pdo_connect($server=NULL, $user=NULL, $pass=NULL, $new_link=FALSE, $client_flags=0x0000, $pconnect=0x0000) {
     
     // get params
     $server or $server = ini_get("mysql.default_host");
     $user or $user = ini_get("mysql.default_user");
     $pass or $pass = ini_get("mysql.default_password");


     // prepare Data Source Name
     $dsn = "mysql:";
     
     // servername contains a socket path
     if (strpos($server, "/")) {
        strpos($server, ":") and $server = substr($server, strpos($server, ":") + 1);
        $dsn .= "unix_socket=$server";
     }
     // or hostname and optional port
     else {
        if (strpos($server, ":")) {
           list($server, $port) = explode($server, ":");
           $dsn .= "host=$server;port=$port";
        }
        else {
           $dsn .= "host=$server";
        }
     }
     //("we don't have a dbname= at this point");
     

     // driver flags
     $flags = array(
        PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => true,
        #PDO::MYSQL_ATTR_INIT_COMMAND => '',   // first SQL command after connect
        #PDO::MYSQL_ATTR_DIRECT_QUERY => true, // direct queries, no prepared statements
        #PDO::MYSQL_ATTR_FOUND_ROWS => true,   // rowCount() for SELECTs, not sure if this is an init parameter, or Statement setting
     );
     if ($client_flags & MYSQL_CLIENT_COMPRESS) {
        $flags[PDO::MYSQL_ATTR_COMPRESS] = 1;
     }
     if ($client_flags & MYSQL_CLIENT_SSL) {
        $flags[PDO::MYSQL_ATTR_SSL_KEY] = "client.pem";
        $flags[PDO::MYSQL_ATTR_SSL_CERT] = "cert.pem";
        $flags[PDO::MYSQL_ATTR_SSL_CA] = "ca.pem";
     }
     if ($client_flags & MYSQL_CLIENT_IGNORE_SPACE) {
        $flags[PDO::MYSQL_ATTR_IGNORE_SPACE] = 1;
     }
     if ($client_flags & 128) {
        $flags[PDO::MYSQL_ATTR_LOCAL_INFILE] = 1;
     }
     if ($pconnect) {
        $flags[PDO::ATTR_PERSISTENT] = 1;
     }
     

     // instantiate connection
     try {
        $pdo = new PDO($dsn, $user, $pass, $flags);
     }
     catch (RuntimeException $pdo) {
        PDO_HELPFUL and pdo_trigger_error("pdo_connect() Failed. {$pdo->getMessage()}", E_USER_WARNING);
        return new pdo_dummy("Database connection had failed [ErrCode{$pdo->getCode()}].");
     }
     
     // set PDO flags
     $pdo->setAttribute(PDO::ATTR_ERRMODE, (PDO_HELPFUL ? PDO::ERRMODE_WARNING : PDO::ERRMODE_SILENT)); //or PDO::ERRMODE_EXCEPTION
     $pdo->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
     $pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
     $pdo->setAttribute(PDO::ATTR_STRINGIFY_FETCHES, false);
     $pdo->setAttribute(PDO::ATTR_CASE, PDO::CASE_NATURAL);
     $pdo->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, true);


     // done     
     return pdo_handle($pdo, "SET_HANDLE_AS_DEFAULT");
  }




  /**
   * CREATE DATABASE
   *
   */
  function pdo_create_db($dbname, $link=NULL) {
     $dbname = str_replace("`", "``", $dbname);
     return (bool)pdo_query("CREATE DATABASE `$dbname`", pdo_handle($link));
  }




  /**
   * Move pointer in result set.
   *
   */
  function pdo_data_seek($stmt, $row_number) {
      !PDO_SEEKABLE and pdo_trigger_error("pdo_data_seek() PDO_MySQL driver does not support cursors. Enable PDO_SEEKABLE.", E_USER_WARNING);
      pdo_stmt($stmt)->fetch(PDO::FETCH_ASSOC, PDO::FETCH_ORI_ABS, $row_number);
  }
  



  /**
   * Return one entry from _list_dbs().
   *
   */
  function pdo_db_name($stmt, $row, $field="Database") {
     return pdo_result($stmt, $row, $field);
  }




  /**
   * Combo of _select_db() and _query().
   *
   */
  function pdo_db_query($dbname, $query, $link=NULL, $params=NULL) {
     PDO_HELPFUL and pdo_trigger_error("pdo_db_query() is redundant. Use pdo_select_db() and pdo_query().", E_USER_DEPRECATED);

     if (pdo_select_db($dbname, pdo_handle($link))) {
        $params = func_get_args();
        array_shift($params);
        return call_user_func_array("pdo_query", $params);
     }
  }




  /**
   * DROP DATABASE
   *
   */
  function pdo_drop_db($dbname, $link=NULL) {
     $dbname = str_replace("`", "``", $dbname);
     return (bool)pdo_query("DROP DATABASE `$dbname`", pdo_handle($link));
  }




  /**
   * Get numeric error code for last failed database query.
   *
   */
  function pdo_errno($link=NULL) {
     $error = pdo_handle($link)->errorInfo();
     return $error[1];
  }




  /**
   * Get error message for last failed request.
   *
   */
  function pdo_error($link=NULL) {
     #
     #### Possibly better to also keep a $pdo_last_stmt to get possible errors from there?
     #    PDO::errorInfo might be empty
     #    Keeping PDO::ERRMODE_WARNING per default isn't as advisable for production setups.
     #
     #    Similar wrapper in https://www.kitware.com/svn/CDash/trunk/cdash/pdocore.php
     #    also just uses PDO::errorInfo
     #
     global $pdo_last_stmt;
     $link = pdo_handle($link);

     # we don't really know what ran last, PDO:: or PDOStatement::
     if (!empty($pdo_last_stmt)) {
        $error = $pdo_last_stmt[spl_object_hash($link)]->errorInfo();
     }
     else {
        $error = $link->errorInfo();
     }
     return $error[2];
  }




  /**
   * String escaping, alias to _real_escape_string()
   *
   */
  function pdo_escape_string($str, $link=NULL) {
     return pdo_real_escape_string($str, $link);
  }




  /**
   * Get result row.
   * Note you still have to use the MYSQL_ constants, _BOTH, _ASSOC, or _NUMeric array.
   *
   */
  function pdo_fetch_array($stmt, $type=3) {
  
     $map = array(
         MYSQL_ASSOC/*1*/ => PDO::FETCH_ASSOC/*2*/,
         MYSQL_NUM/*2*/ => PDO::FETCH_NUM/*3*/,
         MYSQL_BOTH/*3*/ => PDO::FETCH_BOTH/*4*/,
         // no consistency so far, so let's embrace and extend it:
         0=>4, "assoc"=>2, "num"=>3, "both"=>4, "ASSOC"=>2, "NUM"=>3, "BOTH"=>4, "MYSQL_ASSOC"=>2, "MYSQL_NUM"=>3, "MYSQL_BOTH"=>4,
     );
  
     return pdo_stmt($stmt)->fetch(isset($map[$type]) ? $map[$type] : $type);
  }




  /**
   * Get result row.
   * Always an associative array as result.
   *
   */
  function pdo_fetch_assoc($stmt) {
     return pdo_stmt($stmt)->fetch(PDO::FETCH_ASSOC);
  }




  /**
   * Get table attributes/meta for a column.
   * Doesn't match up 1:1.
   *
   * See also http://www.phpcl***es.org/browse/file/47988.html
   * (discovered too late, similar intent except for the class wrapping,
   * the getColumnMeta conversion seems more complete);
   * so maybe lets use _list_fields() / SHOW COLUMNS FROM .. for details
   # Doc ~/php/php-5.5.5/ext/pdo_mysql/mysql_statement.c for PDO types
   *
   */
  function pdo_fetch_field($stmt, $column_id) {
  
     // map meta types to what mysql_fetch_field returned
     $native_map = array(
         "BOOL"=>"bool", "NULL"=>"null", "BLOB"=>"blob",
         "LONG"=>"int", "LONGLONG"=>"int", "BIT"=>"int", "ENUM"=>"int", "DECIMAL"=>"int",
         "VAR_STRING"=>"string", "STRING"=>"string", "VARCHAR"=>"string",
         "YEAR"=>"string",
     );
     $pdo_map = array(
         PDO::PARAM_STR => "string",
         PDO::PARAM_INT => "int",
         PDO::PARAM_BOOL => "bool",
         PDO::PARAM_NULL => "null",
         PDO::PARAM_LOB => "blob",
     );

     // PDO meta field set (no conflicting locals, so extract() will do)
     extract(pdo_stmt($stmt)->getColumnMeta($column_id));
     
     // convert format
     return (object)array(
        "name" => $name,
        "table" => $table,
        "def" => NULL,  // undocumented
        "max_length" => $len,  // PDO reads from ->max_len, but doesn't match up with libmysqls results
        "not_null" => in_array("not_null", $flags),
        "primary_key" => in_array("primary_key", $flags),
        "unique_key" => in_array("unique_key", $flags),
        "multiple_key" => in_array("multiple_key", $flags),
        "numeric" => $native_type == "LONG",
        "blob" => $native_type == "BLOB",
        "type" => isset($native_type) ? $native_map[$native_type] : $pdo_map[$pdo_type],
        "unsigned" => in_array("unsigned", $flags),
        "zerofill" => in_array("zerofill", $flags),
     );
  }




  /**
   * Returns the list of strlen()s for the last result row.
   *
   */
  function pdo_fetch_lengths($stmt) {
  
      // no can do
      if (!PDO_SEEKABLE or !$stmt instanceof PDOStatement_Seekable) {
         pdo_trigger_error("pdo_fetch_lengths() Cannot retrieve the last row to calculate string lengths, no cursor available. Enable PDO_SEEKABLE." . (PDO_HELPFUL ? " Better yet do the field length calculation yourself with <a>array_map('strlen',\$row)</a> on the last pdo_fetch_row()." : ""), E_USER_WARNING);
      }

      // with _Seekable the last row is always cached
      return array_map("strlen", pdo_stmt($stmt)->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_PRIOR));
  }




  /**
   * Get result row as object.
   *
   */
  function pdo_fetch_object($stmt, $classname="stdClass", $params=array()) {
     return pdo_stmt($stmt)->fetchObject($classname, $params);
  }
  



  /**
   * Get result row as indexed list.
   *
   */
  function pdo_fetch_row($stmt) {
     return pdo_stmt($stmt)->fetch(PDO::FETCH_NUM);
  }




  /**
   * _fetch_field() meta data broken up into individual functions.
   *
   */
  function pdo_field_flags($stmt, $col) {
     $meta = pdo_stmt($stmt)->getColumnMeta($col);
     return implode(" ", $meta["flags"]);
  }
  function pdo_field_len($stmt, $col) {
     return pdo_fetch_field($stmt, $col)->max_length;
  }
  function pdo_field_name($stmt, $col) {
     return pdo_fetch_field($stmt, $col)->name;
  }
  function pdo_field_seek($stmt, $col) {
     pdo_trigger_error("pdo_field_seek() Has no effect. Please use the \$col parameter for all pdo_field_*() functions.", E_USER_WARNING);
  }
  function pdo_field_table($stmt, $col) {
     return pdo_fetch_field($stmt, $col)->table;
  }
  function pdo_field_type($stmt, $col) {
     return pdo_fetch_field($stmt, $col)->type;
  }




  /**
   * Unallocating a query result.
   *
   * This call has little practical use.
   * Rather just unset() your pdo_query $result object variables.
   *
   */
  function pdo_free_result($stmt) {
     ###PDO_HELPFUL and trigger_error("pdo_free_result() usage is mostly redundant. PHP cleans up resource handles/objects if you just unset() them, or move out of scope.", E_USER_DEPRECATED);

     // free up some resources
     try {
        pdo_stmt($stmt)->fetchAll();
        pdo_stmt($stmt)->closeCursor();
     }
     catch (PDOException $e) {
        // yeah, let's ignore that
     }

     // unsetting here has no effect on the outer scope
     $stmt = NULL;
  }




  /**
   * Get libmysql/mysqlnd client version.
   *
   */
  function pdo_get_client_info($link=NULL) {
     return pdo_handle($link)->getAttribute(PDO::ATTR_CLIENT_VERSION);
  }




  /**
   * Get Connection: STATUS
   * mostly "Localhost via UNIX socket"
   *
   */
  function pdo_get_host_info($link=NULL) {
     return pdo_handle($link)->getAttribute(PDO::ATTR_CONNECTION_STATUS);
  }
  



  /**
   * MySQL protocol version.
   *
   */
  function pdo_get_proto_info($link=NULL) {
     return pdo_query("SELECT @@protocol_version AS ver", pdo_handle($link))->fetchObject()->ver;
  }




  /**
   * Mysqld/Mariadb server version.
   *
   */
  function pdo_get_server_info($link=NULL) {
     return pdo_query("SELECT VERSION() as version", pdo_handle($link))->fetchObject()->version;
  }




  /**
   * Show last queries.
   *
   * @stub  We don't keep a log currently.
   *
   # See ~/php/php-5.5.5/ext/mysql/php_mysql.c
   # haven't looked up what libmysql does here; presumably PHP keeps the query log
   *
   */
  function pdo_info($link=NULL) {
     return "";
  }




  /**
   * Last inserted ID.
   *
   */
  function pdo_insert_id($link=NULL) {
     return pdo_handle($link)->lastInsertId();
     //pdo_query("SELECT last_insert_id() AS id", $link)->fetchObject()->id;
  }




  /**
   * SHOW DATABASES
   *
   */
  function pdo_list_dbs($link=NULL) {
     return pdo_query("SHOW DATABASES", pdo_handle($link));
  }




  /**
   * Show table definition.
   *
   */
  function pdo_list_fields($dbname, $table, $link=NULL) {
     $dbname = str_replace("`", "``", $dbname);
     $table = str_replace("`", "``", $table);
     return pdo_query("SHOW COLUMNS FROM `$dbname`.`$table`", pdo_handle($link))->fetchAll();
  }




  /**
   * Retrieves the current MySQL server threads.
   *
   */
  function pdo_list_processes($link=NULL) {
     return pdo_query("SHOW FULL PROCESSLIST", pdo_handle($link));
  }




  /**
   * SHOW TABLES result set.
   *
   */
  function pdo_list_tables($dbname, $link=NULL) {
     $dbname = str_replace("`", "``", $dbname);
     return pdo_query("SHOW TABLES FROM `$dbname`", pdo_handle($link));
  }




  /**
   * Number of fields (columns) in the result rows.
   *
   */
  function pdo_num_fields($stmt) {
     return pdo_stmt($stmt)->columnCount();
  }




  /**
   * Amount of results for last SELECT query.
   *
   # See: http://stackoverflow.com/a/883523
   #
   #  * PDOStmt::rowCount() works for UPDATE/INSERT/DELETE,
   #    but also SELECT since pdo_query() sets ::MYSQL_ATTR_FOUND_ROWS then.
   #
   #  * FOUND_ROWS() is a nice alternative,
   #    But only if _num_rows() is called just after the _query() or no
   #    intermediate query was run, no second database connection is open.
   #
   #  * mysql_ did actually use fetchAll()+count()
   #
   */
  function pdo_num_rows($stmt=NULL) {
  
     /* Unsolicited advise; maybe redundant now that there's two fallbacks.
        Users utilizing _num_rows() however are likely to for($i)-iterate over
        the resultset with indexed pdo_result() calls [which won't work].
     */
     //PDO_HELPFUL and pdo_trigger_error("pdo_num_rows() Should be avoided. To get the number of results, instead use \$result->fetchAll() to get the complete row list and just count() it.", E_USER_NOTICE);

     // let's try this anyway
     if ($num = pdo_stmt($stmt)->rowCount()) {
        return $num;
     }
     
     // fallback
     return pdo_query("SELECT FOUND_ROWS() as num")->fetchObject()->num;
  }




  /**
   * Open a persistent PDO connection.
   *
   */
  function pdo_pconnect($server, $user, $pass, $new_link=FALSE, $client_flags=0x0000, $pconnect=0x0000) {
     return pdo_connect($server, $user, $pass, $new_link, $client_flags, $pconnect=TRUE);
  }




  /**
   * Keep connection open.
   * (Doesn't actually do that. But mysqlnd/pdo_mysql implicitly.)
   *
   */
  function pdo_ping($link=NULL) {
     return pdo_query("SELECT 1", pdo_handle($link)) ? true : false;
  }




  /**
   * Run query.
   *
   * Note that this can be invoked with just a SQL string:
   *
   *   pdo_query("SELECT 1,2,3");
   *
   * Or with bound parameters:
   *
   *   pdo_query("SELECT ?,?,?", 1, 2, 3);
   *
   * Or an indexed array of bound parameters:
   *
   *   pdo_query("SELECT :a, :b, :c", $array);
   *
   * And an optional database connection $link either before or after a parameter list:
   *
   *   pdo_query("SELECT 1,?,?", $link, 2, 3);
   *   pdo_query("SELECT 1,?,?", 2, 3, $link);
   *
   */
  function pdo_query($sql, $link=NULL, $params=NULL) {

     // separate params from $sql and $link     
     $params = func_get_args();
     $sql = TRIM( array_shift($params) );
     $flags = array();
     $direct = false;
     

     // find pdo $link     
     if (count($params)) {
        // $link can be the first element
        if (is_object(reset($params))) {
           $link = array_shift($params);
        }
        // or the last
        elseif (is_object(end($params))) {
           $link = array_pop($params);
        }
     }
     // or we use the default $pdo
     $link = pdo_handle($link);

     
     // is $params a list to pdo_query(), or just one array with :key=>value pairs?
     if (count($params)==1 && is_array($params[0])) {
        $params = array_shift($params);
     }


     // add PDO_MySQL driver flag / workaround for specific query types
     switch (strtoupper(substr($sql, 0, strspn(strtoupper($sql), "SELECT,USE,CREATE")))) {

        // ought to make ->rowCount() work
        case "SELECT":
           $flags[PDO::MYSQL_ATTR_FOUND_ROWS] = true;
           break;

        // temporarily disable prepared statement mode for unbindable directives
        case "USE":
           $direct = true;
           $link->setAttribute(PDO::ATTR_EMULATE_PREPARES, true);
           #$flags[PDO::MYSQL_ATTR_DIRECT_QUERY] = true; // has no effect as stmt flag, also overwritten by setAttr EMULATE_PREPARES
           break;

        default:
     }
     
     
     // add syntax notices?
     if (PDO_HELPFUL>=2) {
        strpos($sql, "'") and pdo_trigger_error("pdo_query() It looks like you're still using single ' quotes in your SQL. This indicates plain or interpolated strings or variables in SQL context. Investigate if parameter binding `pdo_query(\"SELECT ?, ?\", \$var1, \$var2)` would fit.");
        strpos($sql, '"') and pdo_trigger_error("pdo_query() You are using double \" quotes in your SQL. Beware that this is ambiguous. In MySQLs default mode these indicate interpolated string variables (don't do that, use bound parameters), while in MySQL ANSI mode they quote identifiers (table or column name).");
     }


     // unparameterized query()
     if ($direct) {
        $stmt = $link->query($sql);
        $link->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
     }
     // or prepare() and execute()
     else {
        if ($stmt = $link->prepare($sql, $flags)) {   // no try-catch in _WARNING mode
           $stmt->execute($params);
        }
     }

     
     // result
     if (!$stmt and PDO_HELPFUL) {
        pdo_trigger_error("pdo_query() SQL query failed, see pdo_error()", E_USER_WARNING);
     }
     elseif (PDO_SEEKABLE & !$direct) {
        return new PDOStatement_Seekable($stmt, $params);
     }
     else {
        return $stmt;
     }
  }




  /**
   * Escape *strings* for use in SQL context.
   *
   * Note that you still need to enclose string values in 'single quotes' when
   * interpolating/concatenating it into queries.
   *
   * And you shouldn't keep using this function, if you already use ? placeholders
   * with separate value parameters to pdo_query().
   *
   */
  function pdo_real_escape_string($str, $link=NULL) {
     return substr(pdo_handle($link)->quote($str), 1, -1);
  }




  /**
   * Return one field from a result row.
   *
   */
  function pdo_result($stmt, $row, $field=0) {
  
     // Scroll to and retrieve the given $row (maybe it's buffered even)
     if (PDO_SEEKABLE) {
        $rows = array(
           $row => pdo_stmt($stmt)->fetch(PDO::FETCH_BOTH, PDO::FETCH_ORI_ABS, $row)
        );
     }
     
     // workaround: fetch everything, works just once
     else {
        pdo_trigger_error("pdo_result() Can currently only be used once, for fetching a value from the first \$row. Scrolling only works with PDO_SEEKABLE enabled.", E_USER_WARNING);

        $rows = pdo_stmt($stmt)->fetchAll(PDO::FETCH_BOTH);
        #static $rows[hash(stmt)]; //would otherwise bind the result set here
     }

     
     // check if found
     if (isset($rows[$row][$field])) {
        return $rows[$row][$field];
     }
     else {
        pdo_trigger_error("pdo_result() Couldn't find row [$row] and column `$field`.");
     }
     
  }




  /**
   * USE database_name;
   *
   */
  function pdo_select_db($dbname, $link=NULL) {
     $dbname = str_replace("`", "``", $dbname);
     return (bool)pdo_query("USE `$dbname`", pdo_handle($link));
  }


  
  
  /**
   * Set charset used for strings from client, in transport, and for result data.
   *
   */
  function pdo_set_charset($charset, $link=NULL) {
     $charset = pdo_handle($link)->quote($charset);
     return (bool)pdo_query("SET NAMES $charset", pdo_handle($link));
  }




  /**
   * Return server status and some settings.
   *
   * @requires: php (>= 5.5) | upgradephp
   */
  function pdo_stat() {
     return array_column(pdo_query("SHOW STATUS")->fetchAll(), "Value", "Variable_name");
  }




  /**
   * SHOW TABLES [$i] after pdo_list_tables()
   *
   */
  function pdo_tablename($stmt, $i) {
     return pdo_result($stmt, $i, 0);
  }




  /**
   * Returns the connection/thread ID.
   * It's unique among all connected clients.
   *
   */
  function pdo_thread_id($link=NULL) {
     return pdo_query("SELECT connection_id() AS id", pdo_handle($link))->fetchObject()->id;
  }




  /**
   * Switch to unbuffered mode before issuing SQL query.
   *
   */
  function pdo_unbuffered_query($sql, $link=NULL, $params=NULL) {
  
     // find optional $link param
     $params = func_get_args();
     $link = array_filter($params, "is_object");
     $link = pdo_handle($link ? reset($link) : NULL);
     $link->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, false);
     
     // invoke real pdo_query()
     $result = call_user_func_array("pdo_query", $params);

     // reset to buffered mode
     $link->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, true);
     
     // done
     return $result;
  }






  ##############################  helper functions  #############################



  
  /**
   * Determine if to use the current PDO $link, or the last used handle
   * which is kept in global `$pdo`;
   *
   */
  function pdo_handle($link, $connect=0) {
     global $pdo;

     // got a PDO handle as parameter already
     if (is_object($link)) {

        // implicitly update
        if ($connect && !is_a($link, "pdo_dummy")) {
           $pdo = $link;
        }
     }
     
     // last used handle
     elseif (isset($pdo) && is_object($pdo)) {
        $link = $pdo;
     }
     
     // not connected yet
     else {
        $link = new pdo_dummy("You don't have an open database connection, but tried to invoke a call anyway.");
     }

     return $link;
  }




  /**
   * Check if statement (result handle) is usable.
   *
   */
  function pdo_stmt($stmt) {

     if (is_object($stmt)) {
        return $stmt;
     }
     else {
        return new pdo_dummy("Your last query was unsuccessful and returned FALSE instead of a fetchable result. See pdo_error() to find out why.");
     }
  }


  
  
  /**
   * Error messages.
   *
   * Augments the actual origin path/filename and linenumber.
   * Adds some HTML prettyfication.
   *
   */
  function pdo_trigger_error($msg, $level=E_USER_NOTICE) {

     // locate source of last pdo_*() invocation
     foreach ((debug_backtrace()) as $src) {
     
        // skip any functions in the current file
        if (empty($src["file"])) {
           $src["file"] = "{main}";
           $src["line"] = "-";
        }
        if ($src["file"] != __FILE__) {
           $dir = dirname($src["file"]);
           $file = basename($src["file"]);
           $msg .= " - caused by $dir/<b>$file</b>, line <b>$src[line]</b>, when calling <a>$src[function]()</a>;";
           break;
        }
     }
     
     // pass on to actual error handler chain
     trigger_error($msg, (($level == 1<<14) && (PHP_VERSION < 5.3)) ? E_USER_NOTICE : $level);
  }



  /**
   * Provide userland faux cursor support. Simply refetches query results
   * for out-of-order seeking. It also implements a configurable-sized
   * cache, but per default just keeps the last row. (PDO_SEEKABLE can be
   * an integer to define the cache length).
   *
   */
  class PDOStatement_Seekable implements Iterator {

     // the actual PDOStatement
     private $stmt = NULL;
     // bound parameters for reexecution
     private $params = array();

     // row cursor
     private $i = -1;
     // available max key / rowcount
     private $max;
     // last fetched rows
     private $cache = array();


     // keep proxied PDOStatement and data necessary to rerun it
     function __construct($stmt, $params) {
        $this->stmt = $stmt;
        $this->params = $params;
        $this->max = $stmt->rowCount(/*PDO::MYSQL_ATTR_FOUND_ROWS*/) - 1;
     }


     // invoke wrapped PDOStatement
     function __call($func, $args) {
        return call_user_func_array(array($this->stmt, $func), $args);
     }


     // repopulate PDOStatement, reset cache and cursor
     function execute($params = NULL) {
        # Superposes the actual stmt::execute(), in case it's really a new query.
        # Note that rewinding also has to reset the cache, in case the table
        # contents changed meanwhile. So may result in a different set of result
        # rows alltogether. Which is really not wanted since this is all just
        # meant for seeking. (No way around that in a userland faux cursor.)
        $this->stmt->execute($params ? $params : $this->params);
        $this->max = $stmt->rowCount(/*PDO::MYSQL_ATTR_FOUND_ROWS*/) - 1;
        $this->i = -1;   // last fetched row
        $this->cache = array();
     }


     // fetch a single row
     function fetch($type=PDO::FETCH_ASSOC, $ori=PDO::FETCH_ORI_NEXT, $offset=0) {


        // calculate offset
        $last = & $this->i;
        $target = array(                                    
            PDO::FETCH_ORI_NEXT => $last + 1,
            PDO::FETCH_ORI_PRIOR => $last,
            PDO::FETCH_ORI_REL => $last + $offset,
            PDO::FETCH_ORI_FIRST => -1,
            PDO::FETCH_ORI_LAST => $this->max,
            PDO::FETCH_ORI_ABS => $offset,
        );
        $target = $target[$ori];
#print "seek($last->$target) ";

        
        // last row? got that covered!
        if (isset($this->cache[$target])) {
#print "seek(==) ";
            return $this->rowType($type, $this->cache[$target]);
        }
        

        // moving farther backwards
        if ($target < $last) {
#print "seek(<<) ";
            $this->execute();
        }

        
        // jump forwards
        while ($target > $last + 1) {
#print "seek(>>) ";
            $row = $this->stmt->fetch(PDO::FETCH_ASSOC);
            $last++;
            if (!$row) {
               return pdo_trigger_error("PDOStatement_Seekable::fetch() Scrolling past last row.", E_USER_WARNING) and $row;
            }
        }


        // actually fetch next row
        if ($row = $this->stmt->fetch(PDO::FETCH_ASSOC)) {
#print "seek(ft) ";
           assert($target == ++$last);
           // keep last row(s)
           if (count($this->cache) > PDO_SEEKABLE) {
              $this->cache = array_slice($this->cache, $last, - PDO_SEEKABLE, true);
           }
           $this->cache[$last] = $row;
        }
        return $this->rowType($type, $row);
     }


     // convert associative array to requested type
     function rowType($type, $row) {
        switch ($row ? $type : false) {
           case             false: return false;
           case    PDO::FETCH_NUM: return array_values($row);
           case   PDO::FETCH_BOTH: return array_merge($row, array_values($row));
           case  PDO::FETCH_ASSOC: return $row;
           case PDO::FETCH_OBJECT: return (object)$row;
        }
     }
     

     // Iterator handling
     function current() {
        return $this->fetch();
     }
     function rewind() {
        if ($this->i >= 0) {
           $this->execute();
        }
     }
     // PDOStatement itself implements just Traversable internally, not Iterator, so we have to handle the keys ourselves
     function key() {
        return $this->i >= 0 ? $this->i : NULL;
     }
     function next() {
        return $this->i + 1;
     }
     function valid() {
        return $this->i < $this->max;
     }


     # fetchAll
     # fetchObject
  }

  

  /**
   * For dummy PDO instances, to avoid fatal Call-to-member-function-on-non-object errors.
   *
   */
  class pdo_dummy {
  
     /**
      * Catch any ->prepare, ->quote, etc. calls when no proper PDO connection
      * or PDOStatement was passed.
      *
      */
     function __call($func, $args) {
        pdo_trigger_error("pdo_dummy::{$func}() {$this->msg}", E_USER_WARNING);
     }

     /**
      * Concretise error message.
      *
      */     
     public $msg;
     function __construct($msg = "You passed an invalid database or result handle..") {
        $this->msg = $msg;
     }
  
  }




  /**
   * Instantiate a placeholder until pdo_connect() was called.
   *
   */
  global $pdo;

  if (!isset($pdo) || !is_object($pdo)) {
     $pdo = new pdo_dummy("You haven't opened a pdo_connect() handle yet.");
  }  // pdo_handle() takes care already, but we could concretise the help message here



}




/**
 * Fallback code for absent/compiled-out mysql_ extension itself.
 * Should PHP 5.7/5.8 remove ext/mysql as surmised, we can just alias
 * the new pdo_* functions back onto mysql_*.
 * Though such unchanged codebases don't benefit from the more flexible
 * function signature / bound params then.
 *
 */
if (!function_exists("mysql_query")) {

   // autogenerated via ReflectionFunction (parameter properties unknown for internal functions)
   function mysql_connect($hostname=NULL, $username=NULL, $password=NULL, $new=NULL, $flags=NULL) { return pdo_connect(func_get_args()); }
   function mysql_pconnect($hostname=NULL, $username=NULL, $password=NULL, $flags=NULL) { return pdo_pconnect(func_get_args()); }
   function mysql_close($link_identifier=NULL) { return pdo_close(func_get_args()); }
   function mysql_select_db($database_name=NULL, $link_identifier=NULL) { return pdo_select_db(func_get_args()); }
   function mysql_query($query=NULL, $link_identifier=NULL) { return pdo_query(func_get_args()); }
   function mysql_unbuffered_query($query=NULL, $link_identifier=NULL) { return pdo_unbuffered_query(func_get_args()); }
   function mysql_db_query($database_name=NULL, $query=NULL, $link_identifier=NULL) { return pdo_db_query(func_get_args()); }
   function mysql_list_dbs($link_identifier=NULL) { return pdo_list_dbs(func_get_args()); }
   function mysql_list_tables($database_name=NULL, $link_identifier=NULL) { return pdo_list_tables(func_get_args()); }
   function mysql_list_fields($database_name=NULL, $table_name=NULL, $link_identifier=NULL) { return pdo_list_fields(func_get_args()); }
   function mysql_list_processes($link_identifier=NULL) { return pdo_list_processes(func_get_args()); }
   function mysql_error($link_identifier=NULL) { return pdo_error(func_get_args()); }
   function mysql_errno($link_identifier=NULL) { return pdo_errno(func_get_args()); }
   function mysql_affected_rows($link_identifier=NULL) { return pdo_affected_rows(func_get_args()); }
   function mysql_insert_id($link_identifier=NULL) { return pdo_insert_id(func_get_args()); }
   function mysql_result($result=NULL, $row=NULL, $field=NULL) { return pdo_result(func_get_args()); }
   function mysql_num_rows($result=NULL) { return pdo_num_rows(func_get_args()); }
   function mysql_num_fields($result=NULL) { return pdo_num_fields(func_get_args()); }
   function mysql_fetch_row($result=NULL) { return pdo_fetch_row(func_get_args()); }
   function mysql_fetch_array($result=NULL, $result_type=NULL) { return pdo_fetch_array(func_get_args()); }
   function mysql_fetch_assoc($result=NULL) { return pdo_fetch_assoc(func_get_args()); }
   function mysql_fetch_object($result=NULL, $class_name=NULL, $ctor_params=NULL) { return pdo_fetch_object(func_get_args()); }
   function mysql_data_seek($result=NULL, $row_number=NULL) { return pdo_data_seek(func_get_args()); }
   function mysql_fetch_lengths($result=NULL) { return pdo_fetch_lengths(func_get_args()); }
   function mysql_fetch_field($result=NULL, $field_offset=NULL) { return pdo_fetch_field(func_get_args()); }
   function mysql_field_seek($result=NULL, $field_offset=NULL) { return pdo_field_seek(func_get_args()); }
   function mysql_free_result($result=NULL) { return pdo_free_result(func_get_args()); }
   function mysql_field_name($result=NULL, $field_index=NULL) { return pdo_field_name(func_get_args()); }
   function mysql_field_table($result=NULL, $field_offset=NULL) { return pdo_field_table(func_get_args()); }
   function mysql_field_len($result=NULL, $field_offset=NULL) { return pdo_field_len(func_get_args()); }
   function mysql_field_type($result=NULL, $field_offset=NULL) { return pdo_field_type(func_get_args()); }
   function mysql_field_flags($result=NULL, $field_offset=NULL) { return pdo_field_flags(func_get_args()); }
   function mysql_escape_string($string=NULL) { return pdo_escape_string(func_get_args()); }
   function mysql_real_escape_string($string=NULL, $link_identifier=NULL) { return pdo_real_escape_string(func_get_args()); }
   function mysql_stat($link_identifier=NULL) { return pdo_stat(func_get_args()); }
   function mysql_thread_id($link_identifier=NULL) { return pdo_thread_id(func_get_args()); }
   function mysql_client_encoding($link_identifier=NULL) { return pdo_client_encoding(func_get_args()); }
   function mysql_ping($link_identifier=NULL) { return pdo_ping(func_get_args()); }
   function mysql_get_client_info() { return pdo_get_client_info(func_get_args()); }
   function mysql_get_host_info($link_identifier=NULL) { return pdo_get_host_info(func_get_args()); }
   function mysql_get_proto_info($link_identifier=NULL) { return pdo_get_proto_info(func_get_args()); }
   function mysql_get_server_info($link_identifier=NULL) { return pdo_get_server_info(func_get_args()); }
   function mysql_info($link_identifier=NULL) { return pdo_info(func_get_args()); }
   function mysql_set_charset($charset_name=NULL, $link_identifier=NULL) { return pdo_set_charset(func_get_args()); }
   function mysql_fieldname($result=NULL, $field_index=NULL) { return pdo_fieldname(func_get_args()); }
   function mysql_fieldtable($result=NULL, $field_offset=NULL) { return pdo_fieldtable(func_get_args()); }
   function mysql_fieldlen($result=NULL, $field_offset=NULL) { return pdo_fieldlen(func_get_args()); }
   function mysql_fieldtype($result=NULL, $field_offset=NULL) { return pdo_fieldtype(func_get_args()); }
   function mysql_fieldflags($result=NULL, $field_offset=NULL) { return pdo_fieldflags(func_get_args()); }
   function mysql_selectdb($database_name=NULL, $link_identifier=NULL) { return pdo_selectdb(func_get_args()); }
   function mysql_freeresult($result=NULL) { return pdo_freeresult(func_get_args()); }
   function mysql_numfields($result=NULL) { return pdo_numfields(func_get_args()); }
   function mysql_numrows($result=NULL) { return pdo_numrows(func_get_args()); }
   function mysql_listdbs($link_identifier=NULL) { return pdo_listdbs(func_get_args()); }
   function mysql_listtables($database_name=NULL, $link_identifier=NULL) { return pdo_listtables(func_get_args()); }
   function mysql_listfields($database_name=NULL, $table_name=NULL, $link_identifier=NULL) { return pdo_listfields(func_get_args()); }
   function mysql_db_name($result=NULL, $row=NULL, $field=NULL) { return pdo_db_name(func_get_args()); }
   function mysql_dbname($result=NULL, $row=NULL, $field=NULL) { return pdo_dbname(func_get_args()); }
   function mysql_tablename($result=NULL, $row=NULL, $field=NULL) { return pdo_tablename(func_get_args()); }
   function mysql_table_name($result=NULL, $row=NULL, $field=NULL) { return pdo_table_name(func_get_args()); }

   // and the few constants
   define("MYSQL_ASSOC", 1);
   define("MYSQL_NUM", 2);
   define("MYSQL_BOTH", 3);
   define("MYSQL_CLIENT_COMPRESS", 32);
   define("MYSQL_CLIENT_SSL", 2048);
   define("MYSQL_CLIENT_INTERACTIVE", 1024);
   define("MYSQL_CLIENT_IGNORE_SPACE", 256);
                            
}


?>