What is the function_exists method in PHP?

The function_exists() method can be used to check if the function is defined or not. This will check both the user-defined and built-in functions.

Syntax

function_exists(string $functionName): bool

Returns

This method returns true if the function is defined. Otherwise it returns false.

Code

<?php 
  function test(){
  }
  function test2(){
  }
  echo "Is test function exists: ";
  var_dump(function_exists('test'));
  echo "\nIs test2 function exists: ";
  var_dump(function_exists('test2'));
  echo "\nIs strlen built-in function exists: ";
  var_dump(function_exists('strlen'));
  echo "\nIs temp function exists: ";
  var_dump(function_exists('temp'));
?>

Explanation

In the code above,

  • We have created two functions test and test2.

  • We have used the function_exists method to check if the function is defined.

  • This method returns true for the functions test, test2, and strlen (built-in function).

  • This method returns false for the temp function name, because there is no method available with the name temp.

Free AI Mock Interviews
Coding Interview
Coding PatternsFree Interview
Gain insights and practical experience with coding patterns through targeted MCQs and coding problems, designed to match and challenge your expertise level.
System Design
You TubeFree Interview
Learn to design a video streaming platform like YouTube by tackling functional and non-functional requirements, core components, and high-level to detailed design challenges.

Free Resources

License: Creative Commons-Attribution-ShareAlike 4.0 (CC-BY-SA 4.0)