has_filter ( $hook_name, $callback = false )
- (string) hook_name The name of the filter hook.
- (callable|string|array|false) callback Optional. The callback to check for. This function can be called unconditionally to speculatively check a callback that may or may not exist. Default false.
- (bool|int) If `$callback` is omitted, returns boolean for whether the hook has anything registered. When checking a specific function, the priority of that hook is returned, or false if the function is not attached.
- Introduced in WordPress: 2.5.0
- Deprecated in WordPress: —
Checks if any filter has been registered for a hook.When using the `$callback` argument, this function may return a non-boolean value
that evaluates to false (e.g. 0), so use the `===` operator for testing the return value.