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Appendix M. List of Reserved Words

The following is a listing of predefined identifiers in PHP. None of the identifiers listed here should be used as identifiers in any of your scripts. These lists include keywords and predefined variable, constant, and class names. These lists are neither exhaustive or complete.

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.

Table M.1. PHP Keywords

and or xor __FILE__ exception (PHP 5)
__LINE__ array() as break case
class const continue declare default
die() do echo() else elseif
empty() enddeclare endfor endforeach endif
endswitch endwhile eval() exit() extends
for foreach function global if
include() include_once() isset() list() new
print() require() require_once() return() static
switch unset() use var while
__FUNCTION__ __CLASS__ __METHOD__ final (as of PHP 5) php_user_filter (as of PHP 5)
interface (as of PHP 5) implements (as of PHP 5) extends public (as of PHP 5) private (as of PHP 5)
protected (as of PHP 5) abstract (as of PHP 5) clone (as of PHP 5) try (as of PHP 5) catch (as of PHP 5)
throw (as of PHP 5) cfunction (PHP 4 only) old_function (PHP 4 only) this (as of PHP 5) namespace (PHP 6 only)
import (PHP 6 only) goto (PHP 6 only)