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is_callable
(PHP 4 >= 4.0.6, PHP 5, PHP 7)
is_callable — Verify that the contents of a variable can be called as a function
Description
Verify that the contents of a variable can be called as a function. This can check that a simple variable contains the name of a valid function, or that an array contains a properly encoded object and function name.
Parameters
-
var -
The value to check
-
syntax_only -
If set to
TRUEthe function only verifies thatvarmight be a function or method. It will only reject simple variables that are not strings, or an array that does not have a valid structure to be used as a callback. The valid ones are supposed to have only 2 entries, the first of which is an object or a string, and the second a string. -
callable_name -
Receives the "callable name". In the example below it is "someClass::someMethod". Note, however, that despite the implication that someClass::SomeMethod() is a callable static method, this is not the case.
Examples
Example #1 is_callable() example
<?php
// How to check a variable to see if it can be called
// as a function.
//
// Simple variable containing a function
//
function someFunction()
{
}
$functionVariable = 'someFunction';
var_dump(is_callable($functionVariable, false, $callable_name)); // bool(true)
echo $callable_name, "\n"; // someFunction
//
// Array containing a method
//
class someClass {
function someMethod()
{
}
}
$anObject = new someClass();
$methodVariable = array($anObject, 'someMethod');
var_dump(is_callable($methodVariable, true, $callable_name)); // bool(true)
echo $callable_name, "\n"; // someClass::someMethod
?>
Example #2 is_callable() and constructors
As of PHP 5.3.0 is_callable() reports constructors as not being callable. This affects PHP 5 style constructors (__construct) as well as PHP 4 style constructors (i.e. methods with the same name as the class). Formerly, both cases have been considered callable.
<?php
class Foo
{
public function __construct() {}
public function foo() {}
}
var_dump(
is_callable(array('Foo', '__construct')),
is_callable(array('Foo', 'foo'))
);
The above example will output:
bool(false) bool(false)
See Also
- function_exists() - Return TRUE if the given function has been defined
- method_exists() - Checks if the class method exists
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Document created the 30/01/2003, last modified the 26/10/2018
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References
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