PHP 5.4.33 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. 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
abstract (as of PHP 5) and array() as break
case catch (as of PHP 5) cfunction (PHP 4 only) class clone (as of PHP 5)
const continue declare default do
else elseif enddeclare endfor endforeach
endif endswitch endwhile extends final (as of PHP 5)
for foreach function global goto (as of PHP 5.3)
if implements (as of PHP 5) interface (as of PHP 5) instanceof (as of PHP 5)
namespace (as of PHP 5.3) new old_function (PHP 4 only) or private (as of PHP 5)
protected (as of PHP 5) public (as of PHP 5) static switch throw (as of PHP 5)
try (as of PHP 5) use var while xor
Compile-time constants
__CLASS__ __DIR__ (as of PHP 5.3) __FILE__ __LINE__ __FUNCTION__ __METHOD__
__NAMESPACE__ (as of PHP 5.3)
Language constructs
die() echo() empty() exit() eval()
include() include_once() isset() list() require()
require_once() return() print() unset()
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User Contributed Notes 3 notes

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16
martindilling at gmail dot com
1 year 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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15
Chris
1 year 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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0
Bob
5 years ago
There are some cases when you need to use a reserved keyword or language construct as a class method name. In this instance, there is very little chance of namespace conflicts (as the class itself acts as a namespace). If you try to define the method the old way, you will get an unexpected token error.

There is an unobtrusive, and very useful way to use a reserved keyword for a method name. For example, you want to define two class methods 'list' and 'unset' (these two are language builtins and normally not allowed for method names).

<?php
class MyClass
{
   
// Define MyClass::unset() with a different name, e.g. 'rm'
   
public function rm($arg)
    {
       
/* code... */
   
}
   
// Define MyClass::list() with a different name, e.g. 'ls'
   
public function ls($arg = null)
    {
       
/* code... */
   
}
   
// Now define a __call() method (requires PHP > 5.2.3 to take effect)
   
public function __call($func, $args)
    {
        switch (
$func)
        {
            case
'list':
                return
$this->ls((isset($args[0]))? $args[0]: null);
            break;
            case
'unset':
                return
$this->rm($args[0]);
            break;
            default:
               
trigger_error("Call to undefined method ".__CLASS__."::$func()", E_USER_ERROR);
            die ();
        }
    }
}
?>

The only caveat is that to use the long method names, you need PHP > 5.2.3. However, a nice feature is that if you are using an older version than 5.2.3, all of the __call() stuff is ignored and the class will behave as expected (in other words, it degrades gracefully).

You also need to be aware of the methods' expected arguments. MyClass::ls()'s argument is optional, so the extra isset() check is required. If your methods take more arguments, they will need to be manually dereferenced from the $args array, e.g. <?php return $this->my_func($args[0], $args[1], $args[2]);?> for 3 required arguments.

This is a nice trick, and can let you code better APIs for newer versions of PHP. However, if this script is to be run on older PHP installations, be very sure to use the short method names.
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