xemacs and php files editing

[lapin bleu]

Hello,

newbie in php programming, I would like to use xemacs as editor (I use it 
for Tex Latex, and it's great).
But when I load it with a php file, the following message appears :
"File mode specification error (void-variable 
cc-imenu-php-generic-expression)", and there is no php menu loaded.

How to configure xemacs so that the php menu option shoud run correctly ?

Thanks.

JP. LASSALLE