php man page for is_callable

IS_CALLABLE(3)								 1							    IS_CALLABLE(3)

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

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

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
	      o $name
		- The callback function to check

	      o $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.

	      o $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(3) 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, "
";  // 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, "
";  //  someClass::someMethod

	      ?>

SEE ALSO
       function_exists(3), method_exists(3).

PHP Documentation Group 													    IS_CALLABLE(3)