WordPress at a glance
filter is not described

mce_buttons_4 filter-hook . WP 1.0

This filter is documented in wp-includes/class-wp-editor.php

Usage

add_filter( 'mce_buttons_4', 'filter_function_name_2433', 10, 2 );
function filter_function_name_2433( $array, $string ){
	// filter...

	return $array;
}
$array
-
$string
-

Where the hook is called

wp_tinymce_inline_scripts()
mce_buttons_4
_WP_Editors::editor_settings()
mce_buttons_4
wp-includes/script-loader.php 462
$toolbar4 = apply_filters( 'mce_buttons_4', array(), 'classic-block' );
wp-includes/class-wp-editor.php 722
$mce_buttons_4 = apply_filters( 'mce_buttons_4', array(), $editor_id );

Where in WP core the hook is used WordPress

Usage not found.