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is_callable

(PHP 4 >= 4.0.6, PHP 5)

is_callable Verify that the contents of a variable can be called as a function

Description

bool is_callable ( callable $name [, bool $syntax_only = false [, string &$callable_name ]] )

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

name

The callback function to check

syntax_only

If set to TRUE the function only verifies that name might 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.

Return Values

Returns TRUE if name is callable, FALSE otherwise.

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($functionVariablefalse$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($methodVariabletrue$callable_name));  //  bool(true)

echo $callable_name"\n";  //  someClass::someMethod

?>

See Also

add a note add a note

User Contributed Notes 21 notes

up
6
empyone at tiscalinet dot it
8 years ago
To corey at eyewantmedia dot com:

your misunderstanding lies in passing in the naked $object parameter. It is correct for is_callable to return FALSE since you cannot 'call an object', you can only call one of its methods, but you don't specify which one. Hence:

is_callable(array($object, 'some_function'), [true or false], $callable_name)

will yield the correct result.

Notice, though, that a quick test I made (PHP 5.0.4) showed that is_callable incorrectly returns TRUE also if you specify the name of a protected/private method from outside of the context of the defining class, so, as wasti dot redl at gmx dot net pointed out, reflection is the way to go if you want to take visibility into account (which you should for true OOP, IMHO).
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6
jphp at dsf dot org dot uk
8 years ago
bob at theshirdshift:

"function_exists" doesn't do this, no, but "method_exists" works fine, and is still faster than is_callable:

<?php
function doTimes($start, $end)
  {
  
$start_time = explode (" ", $start);
  
$start_time = $start_time[1] + $start_time[0];
  
$end_time = explode (" ", $end);
  
$end_time = $end_time[1] + $end_time[0];
  
$time = $end_time - $start_time;
   return
$time;
  }

class
test
 
{
     function
test()
     {
         return
true;
     }
  }

$test = new test;

$callableIsTrue = false;
$startIsCallable = microtime();
for(
$i = 0; $i < 10000; $i++)
  {
     if(
is_callable(array('test', 'test'))) { $callableIsTrue = true; }
  }
$endIsCallable = microtime();

$existsIsTrue = false;
$startExists = microtime();
for(
$i = 0; $i < 10000; $i++)
  {
     if(
method_exists('test', 'test')) { $existsIsTrue = true; }
  }
$endExists = microtime();

$timeIsCallable = doTimes($startIsCallable, $endIsCallable);
$timeExists    = doTimes($startExists, $endExists);

echo
"<b>is_callable = ".($callableIsTrue ? "TRUE" : "FALSE")."</b>, \n";
echo
"<b>method_exists = ".($existsIsTrue ? "TRUE" : "FALSE")."</b><br>\n";

echo
"<br>Did 10000 is_callables in ".$timeIsCallable." seconds";
echo
"<br>Did 10000 method_exists in ".$timeExists." seconds";
?>

is_callable = TRUE, method_exists = TRUE

Did 10000 is_callables in 0.410346984863 seconds
Did 10000 method_exists in 0.175447940826 seconds
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6
np dot liamg at gmail dot com
1 year ago
is_callable() will try __autoload(), if have one.
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3
Andy at txtNation dot com
3 years ago
Note that is_callable is aware of context, and you can ask it things like parent::__construct from within a child constructor

<?php

   
class TestClass extends TestClassParent {
   
       
/** @brief Object initialisation callback
            @returns void */
       
public function __construct() {

           
# do initialisation

            # ...

            # if we have a parent
           
           
if(is_callable('parent::__construct')) {
           
               
# then bubble up
               
               
parent::__construct();
            }
        }
    }
?>
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3
Rafael M. Salvioni
6 years ago
The PHP's function is_callable not verify the visibility of the tested method.

The following function uses the Reflection classes of the PHP5 to check it.

<?php

/**
* Function is_callback().
*
* @param mixed $var Var
* @return bool
*/
function is_callback($var)
{
    if (
is_array($var) && count($var) == 2) {
       
$var = array_values($var);
        if ((!
is_string($var[0]) && !is_object($var[0])) || (is_string($var[0]) && !class_exists($var[0]))) {
            return
false;
        }
       
$isObj = is_object($var[0]);
       
$class = new ReflectionClass($isObj ? get_class($var[0]) : $var[0]);
        if (
$class->isAbstract()) {
            return
false;
        }
        try {
           
$method = $class->getMethod($var[1]);
            if (!
$method->isPublic() || $method->isAbstract()) {
                return
false;
            }
            if (!
$isObj && !$method->isStatic()) {
                return
false;
            }
        } catch (
ReflectionException $e) {
            return
false;
        }
        return
true;
    } elseif (
is_string($var) && function_exists($var)) {
        return
true;
    }
    return
false;
}

?>
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4
corey at eyewantmedia dot com
9 years ago
I've been spending a month on and off trying to figure out why

is_callable($object, [true or false], $varContainingFunctionName)

returned false when it should not have (ie: $object->FunctionName() was callable), I realized I must have misunderstood its purpose. If you find yourself in the same situation, try

function_exists(string functionname)

or

method_exists ( object object, string method_name )

before you rip your hair out :)
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2
passivesmoking AT yahoo DOT com
2 years ago
is_callable doesn't seem able to resolve namespaces.  If you're passing a string, then the string has to include the function's full namespace. 

<?php
namespace foo\bar\baz;

function
something ()
{
    return (
42);
}

var_dump (is_callable ('something')); // false
var_dump (is_callable ('foo\bar\baz\something')); // true
?>

It's easy to forget, but if you just prepend __NAMESPACE__ to your function name strings you should be fine in most cases.
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2
mcroghan at digitalkeg dot com
9 years ago
Be careful when using this function and __call (PHP5).  This function will always report true when using __call.

Need a specific function for the purpose of checking if a class method exists explicitly even when using __call.

Haven't ruled out the possibility of the existence of such a function yet.  So if someone knows of one, please point it out.
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2
juand at softwarecubes dot com
5 years ago
Revised function with static support:

<?php
   
/**
    * The is_callable php function only considers methods declared in the class itself, and ignores the parent's.
    * This version considers all of the hierarchy.
    *
    * @param (string|Object) $class_name
    * @param string $method_name
    * @param bool $static the method being tested is static.
    */
   
public static function isCallable( $class_name, $method_name, $static = false ){
       
        if( !
is_string( $class_name ) ){
           
$class_name = get_class( $class_name );
        }
       
       
// Define Callable
       
if( $static ){
           
$callable = "{$class_name}::{$method_name}";
        }else{
           
$callable = array( $class_name, $method_name );
        }
       
       
       
// Check class itself
           
if( @is_callable( $callable ) === true ){
                if(
$method_name == 'setEmailAddressTypeHash' ) {
                   
ErrorHandler::preDump($callable);
                }
                return
true;
            }
       
       
// Check all parents
           
while( $parent_class = get_parent_class( $class_name ) ){
                if( @
is_callable( $callable ) === true ){
                    return
true;
                }
               
$class_name = $parent_class;
            }
           
        return
false;
    }
?>
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1
Athari
2 years ago
For closures, the function will return true and $callable_name will be set to "Closure::__invoke".
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1
wowkise at gmail dot com
1 year ago
beware calling is_callable on class that has the same method name will return false, i filed a bug report to be included in function description as example

<?php
class test {
function
test() {
}
}
$class = new test();
var_dump(is_callable([$class, 'test']));
?>

will return false
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1
bob at thethirdshift dot net
10 years ago
I, too, was wondering whether is_callable or function exists is faster when checking class methods.  So, I setup the following test:

<?php
function doTimes($start, $end)
  {
   
$start_time = explode (" ", $start);
   
$start_time = $start_time[1] + $start_time[0];
   
$end_time = explode (" ", $end);
   
$end_time = $end_time[1] + $end_time[0];
   
$time = $end_time - $start_time;
    return
$time;
  }

class
test
 
{
      function
test()
      {
          return
true;
      }
  }
 
$callableIsTrue = false;
$startIsCallable = microtime();
for(
$i = 0; $i < 10000; $i++)
  {
      if(
is_callable(array('test', 'test'))) { $callableIsTrue = true; }
  }
$endIsCallable = microtime();

$existsIsTrue = false;
$startExists = microtime();
for(
$i = 0; $i < 10000; $i++)
  {
      if(
function_exists('test::test')) { $existsIsTrue = true; }
  }
$endExists = microtime();

$timeIsCallable = doTimes($startIsCallable, $endIsCallable);
$timeExists     = doTimes($startExists, $endExists);

echo
"<b>is_callable = ".($callableIsTrue ? "TRUE" : "FALSE")."</b>, \n";
echo
"<b>function_exists = ".($existsIsTrue ? "TRUE" : "FALSE")."</b><br>\n";

echo
"<br>Did 10000 is_callables in ".$timeIsCallable." seconds";
echo
"<br>Did 10000 function_exists in ".$timeExists." seconds";
?>

This gives the output :

is_callable = TRUE, function_exists = FALSE

Did 10000 is_callables in 0.0640790462494 seconds
Did 10000 function_exists in 0.0304429531097 seconds

So the fact that function_exists is twice as fast is slightly over shadowed by the fact that it doesn't work on class methods, at least not as far as I can tell.
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0
colin
3 years ago
I haven't seen anyone note this before, but is_callable will correctly determine the existence of methods made with __call. The method_exists function will not.

Example:
<?php

class Test {

    public function
testing($not = false) {
       
$not = $not ? 'true' : 'false';
        echo
"testing - not: $not<br/>";
    }
   
    public function
__call($name, $args) {
        if(
preg_match('/^not([A-Z]\w+)$/', $name, $matches)) {
           
$fn_name = strtolower($matches[1]);
            if(
method_exists($this, $fn_name)) {
               
$args[] = true; // add NOT boolean to args
               
return call_user_func_array(array($this, $matches[1]), $args);
            }
        }
        die(
"No method with name: $name<br/>");
    }

}

$t = new Test();
$t->testing();
$t->notTesting();

echo
"exists: ".method_exists($t, 'notTesting').'<br/>';
echo
"callable: ".is_callable(array($t, 'notTesting'));

?>

Output:

testing - not: false
testing - not: true
exists:
callable: 1
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0
Constantin Kpplinger
4 years ago
It seems the only issue left with is_callable() is the disable_functions ini-setting. Apart from that, is_callable() will reliably evaluate whether the passed function or method can be called from within the same context is_callable() was called from, taking visibility and inheritance into account. This includes functions, regular and static methods, magic functions and methods and implemented interfaces (which are regular methods within the implementing class anyway).

<?php
function regular_function() {}

abstract class
ParentTest
{
    public function
public_parent_method() {}
    protected function
protected_parent_method() {}
    public static function
static_method() {}
    protected static function
protected_static_method() {}
}

class
CallableTest extends ParentTest implements Countable
{
    public function
__invoke() { } // Introduced in 5.3, see http://php.net/manual/language.oop5.magic.php
   
protected function protected_method() { }
    public function
is_callable($args)
    {
        return
is_callable($args);
    }
   
// Countable
   
public function count()
    {
        return
1;
    }
}

$o = new CallableTest();

// Regular function:
var_dump(is_callable('regular_function')); // true

// Magic __invoke method:
var_dump(is_callable($o)); // true if PHP >= 5.3, false otherwise

// Countable implementation (regular method really):
var_dump(is_callable(array($o, 'count'))); // true

// Protected method from outside the object's scope:
var_dump(is_callable(array($o, 'protected_method'))); // false

// Protected method from inside the object's scope via public proxy method:
var_dump($o->is_callable(array($o, 'protected_method'))); // true

// Parent's public method
var_dump(is_callable(array($o, 'public_parent_method'))); // true

// Parent's protected method
var_dump(is_callable(array($o, 'protected_parent_method'))); // false

// Parent's protected method via proxy
var_dump($o->is_callable(array($o, 'protected_parent_method'))); // true

// Parent's static public method
var_dump(is_callable('CallableTest::static_method')); // true

// Parent's static protected method
var_dump(is_callable('CallableTest::protected_static_method')); // false

// Parent's static protected method via proxy
var_dump($o->is_callable('CallableTest::protected_static_method')); // true
?>

Tested PHP versions were 5.2.9 on openSUSE 10.3 (x64) and 5.3.1 on Windows Server 2003 (x86).
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0
Quis strrev TA omicidio strrev TOD com
6 years ago
is_callable() does _not_ check wheter this function is disabled by php.ini's disable_functions

use:

<?PHP
function is_disabled($function) {
 
$disabled_functions=explode(',',ini_get('disable_functions'));
  return
in_array($function, $disabled_functions);
}
?>

I`m running PHP 5.2.4
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0
mw at NO-SPAM hire mason wolf dot com
6 years ago
As empyone noted, early versions of php 5 incorrectly returned true if is_callable checked on a protected or private method. Later versions of php 5 will now only return true if the method is public and can be called externally. I do not know precisely when this behavior was changed, so you may have to test on your own. But sometime between 5.0.4, which empyone said he was using, and 5.2.4 where I tested it myself, the behavior was modified.
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0
hcblue
8 years ago
True that method_exists() is faster than is_callable(). However, is_callable() will be able to correctly recognize method calls handled by __call() in PHP 5, while method_exists() will not.
up
0
wasti dot redl at gmx dot net
8 years ago
The way to discover whether a method exists in face of a __call is reflection.

It should be mentioned that although array('Test', 'func') is callable according to this function (where func is a public static method of Test), actually calling this construct as $fn() fails.
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-1
fgm at osinet dot fr
3 years ago
Note that, for the purpose of this function, an abstract method, although necessarily non-callable since it does not have a body, is still considered to be callable:

<?php
abstract class Foo {
  abstract function
bar();
}

echo
is_callable(array('Foo', 'bar'));
// display: 1
?>
up
-1
rahadotaboulfethatgmail.com
6 years ago
is_callable generates an [E_STRICT] error if the  tested method cannot be called staticly. (and returns the good value)

I used @is_called
i'm using php 5.2.1
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-2
yetanotheruser at hotmail etc
8 years ago
I have come across a strange oddity in versions around the 4.3.11 mark - I may have missunderstood the purpose of this function but hope this'll be helpful for some.

The point the code below is supposed to illustrate is that in some cases with

    <? $myFunc = Array( $myObj, 'myMethod' ); ?>

    <? is_callable( $myFunc, true, $callMe ); ?>

will return true, and give you $callMe set to myObj::myMethod but calling

    <? $callMe(); ?>

doesn't work... however calling

    <? $myFunc[0]->$myFunc[1](); ?>

seems to work fine..

... the reason all the code is down there is I think this oddity is due to how/the order in which I've instantiated my classes or something...

anyhow... HTH someone! :-)

Code follows:

FILE 1 :
<?
   
include('myTools');
   
   
$foo = new myClass();
   
    print
$foo->getMySource();
   
    class
myClass{
       
        var
$flibble = 'wibble';
       
        function
myClass(
           
// Initialise loads of stuff.. including..
           
$this->tools = new myTools();
        )
       
        function
getMySource(){
           
// This just returns the source.. ok, like some HTML to go into an email for example.
            // Some arguments;
           
$args   = $this->flibble;
           
// Call our Tool that returns the source..
           
$source = $this->tools->returnSource( Array ( $this, 'someHTML' ), $args );
           
// and return it..
           
return ( $source );
        }
       
        function
someHTML($args){
           
// Leave PHP
           
?>
            Here is some HTML.. that we want to build outside a PHP block,
            possibly just cos it's tidier in <B>your favourite text editor</B>..
            .. or you want this function to be elsewhere.. for your designers
            to play with etc.. ... incidentally I'd like to say "<?=$args?>" etc.
            <?
           
// .. and we're back.
       
}
    }
   
?>

FILE 2:

<?
   
/* OK - this is some other big library and a whole load more
       faff but this is the particular function in question... it
       just calls the function it's been asked to and uses an output
       buffer to grab the output and return it as a string rather than
       letting it go to terminal/browser.... useful for grabbing PHP pages
       for spidering, emailing etc. etc. etc..
    */
   
   
class myTools(){
       
        function
returnSource($func, $args){
           
            if (
is_callable ( $func, true, $callMe ){
               
// Start a buffer
               
ob_start();
               
// Calling the function like this DOESN'T seem to work:
                // ~~~~~~~~
                // "Command not found : myClass::someHTML"
                // $callMe($args);
                // ~~~~~~~~
                // But - what I've discovered is that this behaves fine..
               
if ( is_array($func) ){
                   
$func[0]->$func[1]($args);
                } else {
                   
$func($args);
                }
               
// Then we just carry on with our code..
               
$rtn =     ob_get_contents();
               
ob_clean();
                return (
$rtn );
            } else {
               
error_log("Doh!");
            }
        }
    }
   
?>
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