List of Keywords

These words have special meaning in PHP. Some of them represent things which look like functions, some look like constants, and so on - but they're not, really: they are language constructs. You cannot use any of the following words as constants, class names, function or method names. Using them as variable names is generally OK, but could lead to confusion.

PHP Keywords
__halt_compiler() abstract and array() as
break callable (as of PHP 5.4) case catch class
clone const continue declare default
die() do echo else elseif
empty() enddeclare endfor endforeach endif
endswitch endwhile eval() exit() extends
final for foreach function global
goto (as of PHP 5.3) if implements include include_once
instanceof insteadof (as of PHP 5.4) interface isset() list()
namespace (as of PHP 5.3) new or print private
protected public require require_once return
static switch throw trait (as of PHP 5.4) try
unset() use var while xor
Compile-time constants
__CLASS__ __DIR__ (as of PHP 5.3) __FILE__ __FUNCTION__ __LINE__ __METHOD__
__NAMESPACE__ (as of PHP 5.3) __TRAIT__ (as of PHP 5.4)