php - Add data attribute to wp_nav_menu -

i have following code:

$nav_menu_args = array('fallback_cb' => '','menu' => 'menu', 'menu_class' => 'menu_class');  $x = wp_nav_menu( apply_filters( 'widget_nav_menu_args', $nav_menu_args, 'menu', $args ) );  $pattern = '#<ul([^>]*)>#i';   $replacement = '<ul$1 data-attr="abc">';  // wrong  echo preg_replace( $pattern, $replacement, $x ); 

i trying add data-attr ul altering pattern, , without making changes through walker_nav_menu.

what want have list this:

<ul class="menu_class" data-attr="abc">   <li><li>   <li>     <ul>       <li></li>     </ul>   <li> </ul> 

but data-attr on inner ul this.

<ul class="menu_class" data-attr="abc">   <li><li>   <li>     <ul data-attr="abc">       <li></li>     </ul>   <li> </ul> 

what missing?

you add number of objects want replace takes first ul.

echo preg_replace( $pattern, $replacement, $x, 1 ); // 1 @ end replace first occurence 

or change items_wrap key of wp_nav_menu.

$nav_menu_args = array('fallback_cb' => '','menu' => 'menu', 'items_wrap' => '<ul class="menu_class" data-attr="abc">%3$s</ul>');