PHP | function_exists() Function
Last Updated :
14 Mar, 2018
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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:
PHP
Output:
PHP
Output:
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";
}
?>
<?php// PHP program to illustrate function_exists()// checking if the in_array() built-in function // exists or notif (function_exists('in_array')) { echo "in_array() function is available.\n";} else{ echo "in_array() function is not available.\n";}?>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";
}
?>
<?php// PHP program to illustrate function_exists()// declaring a function named WelcomeMsgfunction WelcomeMsg(){ echo "Welcome to GeeksforGeeks";}// checking if the function named WelcomeMsg// exists or notif (function_exists('WelcomeMsg')) { echo "WelcomeMsg() function is available.\n";} else{ echo "WelcomeMsg() function is not available.\n";}?>WelcomeMsg() function is available.Reference: http://php.net/manual/en/function.function-exists.php
