function_exists
Return true if the given function has been defined
Description
bool function_exists(string $function)
Parameters
-
function
-
The function name, as a string.
Return Values
Returns true if function exists and is a
function, false otherwise.
Note:
This function will return false for constructs, such as
include_once and echo.
Examples
Example #1 function_exists example
<?php
if (function_exists('imap_open')) {
echo "IMAP functions are available.<br />\n";
} else {
echo "IMAP functions are not available.<br />\n";
}
?>
Notes
Note:
A function name may exist even if the function itself is unusable due to
configuration or compiling options (with the image functions being an example).
See Also
- method_exists
- is_callable
- get_defined_functions
- class_exists
- extension_loaded