function_exists
Function • Params and return types changed in PHP 8.0
Return true if the given function has been defined.
function_exists Function synopsis
function_exists(string $function): boolParameters
$function
Typestring
The function name, as a string.
Return value
Typebool
Returns true if $function exists and is a
function, false otherwise.
This function will return `false` for constructs, such as
[`include_once`](/codex/include_once) and [`echo`](/codex/echo).Changes to the function_exists Function
PHP 8.0
- Return type added:
bool - Parameter name of parameter #1 changed:
$function_nameto$function - Parameter type added for parameter #1 (
$function):string
- function_exists($function_name)
+ function_exists(string $function): boolfunction_exists Function Availability
function_exists Function Availability| PHP Version | Availability |
|---|---|
| PHP 8.6Upcoming Release | Yes |
| PHP 8.5Supported (Latest) | Yes |
| PHP 8.4Supported | Yes |
| PHP 8.3Security-Fixes Only | Yes |
| PHP 8.2Security-Fixes Only | Yes |
| PHP 8.1Unsupported | Yes |
| PHP 8.0Unsupported | Yes |
| PHP 7.4Unsupported | Yes |
| PHP 7.3Unsupported | Yes |
| PHP 7.2Unsupported | Yes |
| PHP 7.1Unsupported | Yes |
| PHP 7.0Unsupported | Yes |
| PHP 5.6Unsupported | Yes |
| PHP 5.5Unsupported | Yes |
| PHP 5.4Unsupported | Yes |
| PHP 5.3Unsupported | Yes |