baeckjens on "Q: Add info to all my 288 pages at once ?"

This works just great:

<?php if( $post->post_parent ) :?>
[ text goes here ]
<?php endif;?>

But when adding this, my footer and sidebar disappear and no text showing:

<?php if( $post->post_parent(308) ) :?>
[ text goes here ]
<?php endif;?>