PHP Check if a variable is a function

PHP

Michael Zippo

To determine if a passed argument is a function or not, here are some of the preferred methods.

Using a function is_callable() :is a built-in function in PHP that is used to check the contents of a variable being called as a function. It can check that a simple variable contains the name of a valid function, or that an array contains a correctly encoded object and a function name. Syntax:
```
bool is_callable ($var_name, $syntx_only, $calbl_name) 
```
Parameters:The is_callable() function takes three parameters as shown in the above syntax and is described below. It is up to the user to use, how many parameters are one, two or three.
- $var_name:the name of the function stored in the string variable $var_name, or an object and name method inside an object.
- $syntx_only:if set to TRUE, the function only checks that the name can be a function or a method. It will reject simple variables that are not strings, or an array that has no valid structure to use as a callback. The valid ones should only have 2 records, the first one being an object or string and the second one - string.
- $calbl_name:gets the name to call. This option is only available for classes.
Return value:This function returns a boolean value. Returns TRUE if $var_name is callable, FALSE otherwise.Example.This example uses the is_callable() functionto check if a parameter is a function or not. // Declare the variable and initialize // with function $function = function () { echo ’GeeksForGeeks’ ; }; // Function check is_callable contains // function or not if ( is_callable ( $function )) { echo "It is function " ; } else { echo " It is not function " ; } // Declare a variable and // initialize this $var = "GeeksForGeeks" ; echo "" ; // Function check is_callable contains // function or not if ( is_callable ( $var )) { echo "It is function " ; } else { echo " It is not function " ; } ?> Exit:It is function It is not function

 instanceof:PHP’s instanceof operator is used to find out if an object is an instance of a class. Syntax: $f instanceof Class_Name 
 Operands:it contains two operands, which are listed below: $f:is used as an object.
 Class_Name:is used to store the class name.
 Returned value: ReturnsTrue if the object belongs to this class or has this class as one of its parents, otherwise it will return False.Example. Inthis example uses the instanceofoperator to determine if a variable is a function in PHP.      
  // Declare a variable and initialize 
  // with function $func  =  function () {   echo  ’GeeksforGeeks’ ; };  
  // Use instanceof to check that it contains 
  // function or not if  (  $func  instanceof  Closure) {   echo  "function" ; }  else  {   echo " not a function " ; }  
  // Declare a variable and initialize it $var  =  "GFG" ;  echo  "" ;  
  // Use instanceof to check that it contains 
  // function or not if  (  $var  instanceof  Closure) {   echo  "function" ; }  else  {   echo " not a function " ; } 
 ?>  Exit:function not a function 
 Example:This example uses the methods  function_exist()  and  is_object()  to check if the argument is a function or not.        
  // Declare the function function  myFun() {   echo  ’GeeksforGeeks’ ; };  
  // Determine if the variable is a function  function  is_function (  $func ) {   return  (  is_string  (  $func ) & amp; & amp; function_exists (  $func ))   || (  is_object  (  $func ) & amp; & amp; (  $func  instanceof  Closure) ); }   echo  is_function (  ’myFun’ );  
 ?>  Exit:1

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PHP Check if a variable is a function

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