Trying to get lowest priority number in WordPress - wordpress

Question

Hello I am trying to get lowest priority number from all the functions that hook into wp_head.
My code is this.
function wpcrown_wpcss_loaded() {
global $wp_filter;
$lowest_priority = max(array_keys($wp_filter['wp_head']));
add_action('wp_head', 'wpcrown_wpcss_head', $lowest_priority + 1);
$arr = $wp_filter['wp_head'];
}
add_action('wp_head', "wpcrown_wpcss_loaded");
But its shown error like this.
Warning: array_keys() expects parameter 1 to be array
Warning: max() [<a href='function.max'>function.max</a>]: When only one parameter is given, it must be an array in
Please help to solve this.
Thanks

Answer 1

As Benoti said $wp_filter is no longer an array so array_keys is throwing these warnings because expects an array.
If you want to add scripts / styles / whatever you have in wpcrown_wpcss_head at the end of the head (to give priority) this should work:
1) Comment this action:
// add_action('wp_head', "wpcrown_wpcss_loaded");
2) Use this one instead:
add_action('wp_head', "wpcrown_wpcss_head");
Hope it helps.

Answer 2

Be carefull on the use of $wp_filters as an array since WordPress 4.7,
Here is the guidelines for wp .4.,7
Make.wordpress that explain:
If your plugin directly accesses the $wp_filter global rather than using the public hooks API, you might run into compatibility issues.
Case 1: Directly setting callbacks in the $wp_filter array
$wp_filter['save_post'][10]['my_special_key'] = array( 'function' => 'my_callback_function', 'accepted_args' => 2 );
This will no longer work, and will cause a fatal error. $wp_filter['save_post'] is no longer a simple array. Rather, it is an object that implements the ArrayAccess interface.
You have two options to work around. The first (and preferred) method is to use the add_filter() or add_action() functions.
add_action( 'save_post', 'my_callback_function', 10, 2 );
If, for some reason, you absolutely cannot, you can still work around this.
if ( ! isset( $wp_filter['save_post'] ) ) {
$wp_filter['save_post'] = new WP_Hook();
}
$wp_filter[ 'save_post' ]->callbacks[10]['my_special_key'] = array( 'function' => 'my_callback_function', 'accepted_args' => 2 );
Case 2: Directly unsetting callbacks in the $wp_filter array
unset( $wp_filter['save_post'][10][ $my_callback_id ] );
This will fail for the same reason as case one. To work around, you can use the standard remove_filter() / remove_action() functions.
remove_action( 'save_post', 'my_callback_function', 10, 2 );
Or, if you absolutely must access the array directly:
if ( isset( $wp_filter[ 'save_post' ] ) ) {
unset( $wp_filter['save_post']->callbacks[10][ $my_callback_id ] );
}
Case 3: Checking if a hook is an array
if ( isset( $wp_filter['save_post'] ) && is_array( $wp_filter['save_post'] ) ) {
// do something
}
This will always return false. $wp_filter['save_post'] is a WP_Hook object. To check if a hook has callbacks, use has_action() or has_filter()
if ( has_action( 'save_post' ) ) {
// do something
}
Case 4: Moving the $wp_filter array pointer manually
If you’re calling next() or prev() on the $wp_filter array pointer to manually manage the order that callbacks are called in (or if you’re doing it to work around #17817), you will likely be unsuccessful. Use callback priorities, add_action() / add_filter(), and remove_action() / remove_filter() appropriately and let WordPress manage execution order.