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.