function_exists
Return TRUE if the given function has been defined
Description
bool function_exists
( string $function_name
)
Parameters
-
function_name
-
The function name, as a string.
Return Values
Returns TRUE if function_name 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