note 110163 added to function.function-exists

You can use this function to conditionally define functions, see: http://php.net/manual/en/functions.user-defined.php For instance Wordpress uses it to make functions "pluggable." If a plugin has already defined a pluggable function, then the WP code knows not to try to redefine it. But function_exists() will always return [b]true[/b] unless you wrap any later function definition in a conditional clause, like if(){...}. This is a subtle matter in PHP parsing. Some examples: <?php if (function_exists('foo')) { print "foo defined\n"; } else { print "foo not defined\n"; } function foo() {} if (function_exists('bar')) { print "bar defined\n"; } else { print "defining bar\n"; function bar() {} } print "calling bar\n"; bar(); // ok to call function conditionally defined earlier print "calling baz\n"; baz(); // ok to call function unconditionally defined later function baz() {} qux(); // NOT ok to call function conditionally defined later if (!function_exists('qux')) { function qux() {} } ?> Prints: foo defined defining bar calling bar calling baz PHP Fatal error: Call to undefined function qux() Other comments here about this (referencing user "eddiec") are mostly correct. Any oddities are probably due to the order in which you include/require files. ---- Server IP: 69.147.83.199 Probable Submitter: 74.4.243.172 ---- Manual Page -- http://www.php.net/manual/en/function.function-exists.php Edit -- https://master.php.net/note/edit/110163 Del: integrated -- https://master.php.net/note/delete/110163/integrated Del: useless -- https://master.php.net/note/delete/110163/useless Del: bad code -- https://master.php.net/note/delete/110163/bad+code Del: spam -- https://master.php.net/note/delete/110163/spam Del: non-english -- https://master.php.net/note/delete/110163/non-english Del: in docs -- https://master.php.net/note/delete/110163/in+docs Del: other reasons-- https://master.php.net/note/delete/110163 Reject -- https://master.php.net/note/reject/110163 Search -- https://master.php.net/manage/user-notes.php