PHP 8.3.4 Released!

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. The following words cannot be used as constants, class names, or function names. They are, however, allowed as property, constant, and method names of classes, interfaces and traits, except that class may not be used as constant name.

PHP Keywords
__halt_compiler() abstract and array() as
break callable case catch class
clone const continue declare default
die() do echo else elseif
empty() enddeclare endfor endforeach endif
endswitch endwhile eval() exit() extends
final finally fn (as of PHP 7.4) for foreach
function global goto if implements
include include_once instanceof insteadof interface
isset() list() match (as of PHP 8.0) namespace new
or print private protected public
readonly (as of PHP 8.1.0) * require require_once return static
switch throw trait try unset()
use var while xor yield
yield from        

* readonly may be used as function name.

Compile-time constants
__CLASS__ __DIR__ __FILE__ __FUNCTION__ __LINE__ __METHOD__
__NAMESPACE__ __TRAIT__
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User Contributed Notes 4 notes

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28
martindilling at gmail dot com
10 years ago
RegEx to find all the keywords:

\b(
(a(bstract|nd|rray|s))|
(c(a(llable|se|tch)|l(ass|one)|on(st|tinue)))|
(d(e(clare|fault)|ie|o))|
(e(cho|lse(if)?|mpty|nd(declare|for(each)?|if|switch|while)|val|x(it|tends)))|
(f(inal|or(each)?|unction))|
(g(lobal|oto))|
(i(f|mplements|n(clude(_once)?|st(anceof|eadof)|terface)|sset))|
(n(amespace|ew))|
(p(r(i(nt|vate)|otected)|ublic))|
(re(quire(_once)?|turn))|
(s(tatic|witch))|
(t(hrow|r(ait|y)))|
(u(nset|se))|
(__halt_compiler|break|list|(x)?or|var|while)
)\b
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18
Thomas Hansen
7 years ago
Please note that reserved words are still not allowed to be used as namespace or as part of it:

<?php
namespace MyNameSpace\List;

class
Test
{
}
?>

This will fail with a Parse error: syntax error, unexpected 'List' (T_LIST), expecting identifier (T_STRING)
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16
Chris
11 years ago
Here they are as arrays:

<?php
$keywords
= array('__halt_compiler', 'abstract', 'and', 'array', 'as', 'break', 'callable', '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', 'if', 'implements', 'include', 'include_once', 'instanceof', 'insteadof', 'interface', 'isset', 'list', 'namespace', 'new', 'or', 'print', 'private', 'protected', 'public', 'require', 'require_once', 'return', 'static', 'switch', 'throw', 'trait', 'try', 'unset', 'use', 'var', 'while', 'xor');

$predefined_constants = array('__CLASS__', '__DIR__', '__FILE__', '__FUNCTION__', '__LINE__', '__METHOD__', '__NAMESPACE__', '__TRAIT__');
?>

Along with get_defined_functions() and get_defined_constants(), this can be useful for checking eval() statements.
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-56
Johnny D.
3 years ago
const FORBIDDEN_TYPES = [
'null',

'bool',
'false',
'true',

'int',
'float',

'string',
];
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