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filter is not described

mce_buttons_4 filter-hook . WP 2.5.0

Filters the fourth-row list of TinyMCE buttons (Visual tab).

Usage

add_filter( 'mce_buttons_4', 'filter_function_name_6255', 10, 2 );
function filter_function_name_6255( $mce_buttons_4, $editor_id ){
	// filter...

	return $mce_buttons_4;
}
$mce_buttons_4(array)
Fourth-row list of buttons.
$editor_id(string)
Unique editor identifier, e.g. 'content'. Accepts 'classic-block' when called from block editor's Classic block.

Changelog

Since 2.5.0 Introduced.
Since 3.3.0 The $editor_id parameter was added.

Where the hook is called

_WP_Editors::editor_settings()
mce_buttons_4
wp_tinymce_inline_scripts()
mce_buttons_4
wp-includes/class-wp-editor.php 726
$mce_buttons_4 = apply_filters( 'mce_buttons_4', array(), $editor_id );
wp-includes/script-loader.php 461
$toolbar4 = apply_filters( 'mce_buttons_4', array(), 'classic-block' );

Where in WP core the hook is used

Usage not found!