This is basically what you need to do if you get the following error when trying to ctrl clicka function:

“The resource is not on the build path of a PHP project”

To convert to a PHPEclipse compatible project you basically need to replace the buildSpec and natures sections of the .project file with the following:

<buildSpec>
	<buildCommand>
		<name>net.sourceforge.phpeclipse.parserbuilder</name>
		<arguments>
		</arguments>
	</buildCommand>
</buildSpec>
<natures>
	<nature>net.sourceforge.phpeclipse.phpnature</nature>
</natures>

If you need to convert the other way, or to something else, simply grab the appropriate section from a working project and paste it into the .project file you need to fix.