Let me just preface this with: verdant conventions are better than no standards at all. And there's really nothing newsworthy here.<br>
Due to the ellipses in the PSR-x documents it's however helpful to detail some semantic deviations and oversights.

<style>
  .yes  { background: #bbeebb; }
  .no   { background: #eeccbb; }
  .part { background: #eedd99; }
  td, th { text-align: center; }
  td:first-child { text-align: left; font-weight: normal; }
</style>
<table width=100%>
<tr>
  <td style="text-align:left">**Property**
  <th>PHP
  <th>PSR-0
  <th>PSR-4
  <th>shared
<tr>
  <td class=yes>Class autoloading
  <td class=yes>✔
  <td class=yes>✔
  <td class=yes>✔
  <td class=yes>✔
<tr>
  <td>Zero configuration
  <td class=yes>✔
  <td class=yes> ✔
  <td class=no>✘
  <td class=no>✘
<tr>
  <td>Multiple class declarations per script
  <td class=yes>✔
  <td class=no>✘ ¹
  <td class=no>✘ ¹
  <td class=yes>✔
<tr>
  <td>Namespace support
  <td class=yes>✔
  <td class=yes>✔
  <td class=yes>✔
  <td class=yes>✔
<tr>
  <td>Multiple namespaces per file
  <td class=yes>✔
  <td class=no>✘
  <td class=no>✘
  <td class=yes>✔
<tr>
  <td>Specific underscore treatment
  <td class=yes>✘
  <td class=yes> ✔
  <td class=yes>✘
  <td class=yes>✘
<tr>
  <td class=yes>Case-insensitive class identifiers ²
  <td class=yes>✔
  <td class=no>✘
  <td class=no>✘
  <td class=yes>✔
<tr>
  <td>Function names
  <td class=yes>✔
  <td class=no>ⁿ/ₐ
  <td class=no>ⁿ/ₐ
  <td class=yes>✔
<tr>
  <td>Case-variant constants
  <td class=yes>✔
  <td class=no>ⁿ/ₐ
  <td class=no> ⁿ/ₐ
  <td class=part>✘
<tr>
  <td class=yes>Phar package support
  <td class=yes>✔
  <td class=part>✘ ³
  <td class=no>✘
  <td class=yes>✔
<tr>
  <td>Versioned bundles ⁴
  <td class=part>✔
  <td class=no>✘
  <td class=no>✘
  <td class=no>✘
<tr>
</table>

<sup>1</sup> = Impractical, but symlinking dependency-merged class modules would be feasible workaround.<br>
<sup>2</sup> = Not just accidentally on some plattforms or filesystems.<br>
<sup>3</sup> = For most PSR-0 autoloaders one can at least handicraft paths into the namespace registry.<br>
<sup>4</sup> = Not a discreet PHP or Phar feature, and resolving dependencies is certainly still best left with composer, not done at runtime.<br>