D 2014-07-27T16:21:08.903
L db
N text/x-markdown
P 479271f818667534622ec4a99c11f35a2172c48f
U mario
W 3785
<h2>db()</h2>

<kbd>[db.php](artifact/0f8ae0eb995299394f4015b047658c5c9c098f53)</kbd> is a lightweight wrapper for PDO. It allows some flexibility with passing scalar parameters, and adds new placeholders for array binding.


<h3>Placeholders</h3>

<table width=95%>

<tr><th>List params</th>  <th>Expanded</th>  <th>Usage</th></tr>
<tr><td><code>?</code></td>  <td><code>?</code></td>  <td>A single scalar value (as in PDO).</td></tr>
<tr><td><code>??</code></td>  <td><code>?, ?, ?</code></td>  <td>List of scalars.</td></tr>

<tr><th>Named params</th>  <th>&nbsp;</th>  <th>&nbsp;</th></tr>
<tr><td><code>:name</code></td>  <td><code>:name</code></td>  <td>Named parameter (as in PDO).</td></tr>
<tr><td><code>::</code></td>  <td><code>:a, :b, :c</code></td>  <td>Extracts named array into list of named placeholders.</td></tr>
<tr><td><code>:&</code></td>  <td><code>`x`=:x AND `y`=:y</code></td>  <td>Named column = :param comparison conjoined with <code>AND</code>.</td></tr>
<tr><td><code>:|</code></td>  <td><code>`x`=:x OR `y`=:y</code></td>  <td>Named Named column = :param comparison conjoined with <code>OR</code>.</td></tr>
<tr><td><code>:,</code></td>  <td><code>`x`=:x, `y`=:y</code></td>  <td>Named column=:param list, typically for INSERT statements.</td></tr>

<tr><th>Identifiers</th>  <th>&nbsp;</th>  <th>&nbsp;</th></tr>
<tr><td><code>?:</code></td>  <td><code>`a`, `b`, `c`</code></td>  <td>Expands array key names into escaped column identifier list.</td></tr>

<tr><th>Expressions</th>  <th>&nbsp;</th>  <th>&nbsp;</th></tr>
<tr><td><code>:*</code></td>  <td>SQL and args</td>  <td>Takes a list of SQL+parameter pairs. Only interpolates the SQL if the array is non-empty. Allows to nest expressions and complex parameters.</td></tr>
</table>


<h3>Parameter passing</h3>

`db()` takes a SQL query as first parameter, and allows an arbitrary number of indexed or array arguments thereafter.

It will bind function arguments to a single placeholder each:

    db("SELECT ?,?,?", 1, 2, 3)

An array arg will be consumed through complex placeholders:

    db("SELECT ??, ??", array(1, 2, 3), array(4, 5, 6));

For indexed parameterization, the order of arguments needs to associate them exactly with the placeholders; obviously.

For named parameters that's not relevant. They have to be passed as array with alphanumeric indexes, and not literal `db()` arguments, of course:

    db("SELECT ::", array("key"=>1, "var"=>2));

Keys need to be unique currently.


<h3> Result wrapper </h3>

Queries don't return a plain PDO handle. They're wrapped in a `db_result{}`, which still allows iterations:

    foreach (db("SELECT * FROM all") as $row) {

Where dual-access with `->property` or `["array"]` syntax is permitted:

       print $row->value;
       print $row["value"]

But the result set also allows just accessing one column from the first row:

    print db("SELECT value FROM config")->value;

Alternatively the real PDOStatement methods are also accessible:

    db("SELECT * FROM all")->fetchAll()


<h3> Database connection </h3>

Per default `db()` just operates on the globally shared `$db` handle.

The `db_wrap{}` handle is initialized with:

    db(new PDO("sqlite:"));

When calling `db()` without any params, it will return said PDO instance. Thus allowing raw access to the active database through this global wrapper:

    db()->prepare("INSERT INTO tbl VALUES(?,?)")
        ->execute(array(1,2));

<h3> Token binding </h3>

Another common feature of such database wrappers are literal placeholder tokens. `db()` provides them as `{NAME}` syntax, for e.g. table name prefixes.

Declaring them is as easy as:

    $db()->tokens["PREFIX"] = "dbname.";



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