How to determine if a PHP function is available

This article describes how to use the function_exists() function to determine whether or not a function is available for your PHP installation.


You can determine whether or not a PHP function is enabled for your web site by using the function_exists() function.

To determine if a function is available:

1. Create a file that contains the following code. This sample code checks to see if the fsockopen() function is available. To check for another function, change the $function_name variable’s value:

$function_name = “fsockopen”;
if ( function_exists($function_name) ) {
echo “$function_name is enabled”;
else {
echo “$function_name is not enabled”;

2. Save the file as function.php or something similar.

3. Upload the file to your public_html directory.

4. Use your browser to go to, where represents your web site’s domain name. The page displays whether or not the function is enabled for your web site.