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PHP : Function Reference : Variable Handling Functions : is_callable

is_callable

Verify that the contents of a variable can be called as a function (PHP 4 >= 4.0.6, PHP 5)
bool is_callable ( mixed var [, bool syntax_only [, string &callable_name]] )

Example 2590. is_callable() example

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<?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

?>

Related Examples ( Source code ) » is_callable

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Code Examples / Notes » is_callable

hcblue
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.

empyone
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).

wasti dot redl
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.

cipri
is_callable also takes the php.ini "disable_functions" setting into consideration; it will return false for functions that have been disabled by your administrator.

bob
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 = ".($existsIsTrue ? "TRUE" : "FALSE")."</b>
\n";
echo "
Did 10000 is_callables in ".$timeIsCallable." seconds";
echo "
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.

corey
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 :)

yetanotheruser
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!");
}
}
}

?>

jphp
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 = ".($existsIsTrue ? "TRUE" : "FALSE")."</b>
\n";
echo "
Did 10000 is_callables in ".$timeIsCallable." seconds";
echo "
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

mcroghan
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.

mw
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.

webmaster __at__ digitalanime __dot__ nl
<?php
while(list($key,$value)=each($HTTP_POST_VARS))
{
 $tmpVar = 'return isset($' . 'this->' . $key . ');';
 if(is_callable($key) && eval($tmpVar) && trim($value) != "")
 {
 $tmpSet = '$this->set' . ucfirst($key) . "('" . $value . "');";
  eval($tmpSet);
}
}
?>
Why do you use this?
Isn't this a better solvation (or.. Whatever :P)
<?php
foreach($_POST as $key => $value)
{
if(is_callable($key) && isset($this->{$key}) && trim($value != '')
{
 $this->{'set' . ucfirst($key)}($value);
}
}
?>
Tada.. Variable objects, that's what they are..

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