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action is not described

admin_head_(content_func) action-hook . WP 2.5.0

Fires in the admin header for each specific form tab in the legacy (pre-3.5.0) media upload popup.

The dynamic portion of the hook, $content_func, refers to the form callback for the media upload type. Possible values include 'media_upload_type_form', 'media_upload_type_url_form', and 'media_upload_library_form'.

Usage

add_action( 'admin_head_(content_func)', 'action_function_name_9598' );
function action_function_name_9598(){
	// action...
}

Where the hook is called

wp_iframe()
wp-admin/includes/media.php 526
do_action( "admin_head_{$content_func}" );

Where the hook is used (in WP core)

Does not used.