The is_callable() function is an inbuilt function in PHP which is used to verify the contents of a variable can be called as a function. It 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.
Syntax:
bool is_callable ( $variable_name, $syntax_only, $callable_name )
Parameters: The is_callable() function accepts three parameters as shown in above syntax and are described below. It depends on user to use how many parameters one, two or three.
- $variable_name: The name of a function stored in a string variable $variable_name, or an object and the name of a method within the object.
- $syntax_only: If set to TRUE the function only verifies that name might be a function or method. It will 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. This option only implemented for classes.
Return value: This function returns a boolean type value. It returns TRUE if $variable_name is callable, FALSE otherwise.
Below program illustrate the is_callable() function in PHP:
Program 1: Simple variable contains a function
<?php // To check a variable if it can be called // as a function. Â Â // Declare the function function Function_xyz()Â { } Â Â $variable_name = "Function_xyz"; var_dump(is_callable($variable_name, false, $callable_name)); echo $callable_name, "\n"; Â Â // using only-one parameter var_dump(is_callable($variable_name)); ?> |
bool(true) Function_xyz bool(true)
Program 2: Array contains a method
<?php // To check a variable if it can be called // as a function.   // Define class class ClassA {    // Define method   function Method_xyz()   {   }   }   // Object instance $obj = new ClassA();   $variable_name = array($obj, 'Method_xyz');   var_dump(is_callable($variable_name, true, $callable_name));  echo $callable_name, "\n";  ?> |
bool(true) ClassA::Method_xyz
Reference: http://php.net/manual/en/function.is-callable.php
