Vérifier que l'auto complétion syntaxique pour PHP est activé :

Window > Properties
PHP > Editor > Content Assist 
activer "Enable auto activation".

Les inclusions des fichiers à parser et dont Eclipse doit proposer la complétion syntaxique.

.buildpath :

<?xml version="1.0" encoding="UTF-8"?>
<buildpath>
	<buildpathentry kind="src" path=""/>
	<buildpathentry kind="con" path="org.eclipse.php.core.LANGUAGE"/>
</buildpath>

Why does Eclipse code completion not work on some projects?

.project

<natures>
  <nature>org.eclipse.php.core.PHPNature</nature>
 </natures>

Eclipse PDT + Code completion not working at all

Code completion/assist for built-in PHP functions in Eclipse PDT

Problème d'autocomplétion avec Eclipse PDT (fonctions PHP Core non reconnues) Si on enlève <nature>org.eclipse.php.core.PHPNature</nature>, sur le projet : Configure > Add PHP support

How to enable autocomplete/syntax-highlight for PHP core functions in Eclipse?

Working with Content Assist tutorial is to teach you how to use PDT 's Content Assist function in order to write code quickly, easily, and accurately.

Components for PDT