function_exists
(PHP 3>= 3.0.7, PHP 4 )
function_exists -- Return TRUE if the given function has
been defined
Description
bool function_exists ( string function_name)
Checks the list of defined functions, both built-in (internal)
and user-defined, for function_name. Returns TRUE on success
or FALSE on failure.
<?php
if (function_exists('imap_open')) {
echo "IMAP functions are available.<br />\n";
} else {
echo "IMAP functions are not available.<br />\n";
}
?>
Note that 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). Also note that
function_exists() will return FALSE for constructs, such
as include_once() and echo().
See also method_exists() and get_defined_functions().
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