PHP | function_exists() Function


The function_exists() is an inbuilt function in PHP. The function_exists() function is useful in case if we want to check whether a function() exists or not in the PHP script. It is used to check for both built-in functions as well as user-defined functions.

Syntax:

boolean function_exists($function_name) 

Parameter: This function accepts a single parameter $function_name. This is the name of function that we want to search in the list of defined function. This is a string type parameter.

Return Values: This function returns a Boolean value. In case a function with the name $function_name exists it returns TRUE, otherwise it returns FALSE. This function will also return FALSE for constructs like “include_once”, “echo” etc.

Below programs illustrate the function_exists() function in PHP:



Program 1:

<?php
// PHP program to illustrate function_exists()

// checking if the in_array() built-in function 
// exists or not
if (function_exists('in_array')) 
{
    echo "in_array() function is available.\n";
} 
else
{
    echo "in_array() function is not available.\n";
}

?>

Output:

in_array() function is available.

Program 2:

<?php
// PHP program to illustrate function_exists()

// declaring a function named WelcomeMsg
function WelcomeMsg()
{
    echo "Welcome to GeeksforGeeks";
}

// checking if the function named WelcomeMsg
// exists or not
if (function_exists('WelcomeMsg')) 
{
    echo "WelcomeMsg() function is available.\n";
} 
else
{
    echo "WelcomeMsg() function is not available.\n";
}

?>

Output:

WelcomeMsg() function is available.

Reference:
http://php.net/manual/en/function.function-exists.php




Sudipta sahana BTech 2nd year Cse student

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.




Practice Tags :

Recommended Posts:



0 Average Difficulty : 0/5.0
No votes yet.