As @Milo Said. Your function is ended early. Try this for save_post
action.
add_action( 'save_post', 'mob_datebox_save', 1, 2);
function mob_datebox_save( $post, $post_id )
{
// Bail if we're doing an auto save
if( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) return;
// if our nonce isn't there, or we can't verify it, bail
if( !isset( $_POST['meta_box_nonce'] ) || !wp_verify_nonce( $_POST['meta_box_nonce'], 'my_meta_box_nonce' ) ) return;
// if our current user can't edit this post, bail
if( !current_user_can( 'edit_post', $post_id ) ) return;
// now we can actually save the data
$allowed = array(
'a' => array( // on allow a tags
'href' => array() // and those anchors can only have href attribute
)
);
// Make sure your data is set before trying to save it
if( isset( $_POST['mob_datetext'] ) )
update_post_meta( $post_id, 'mob_datetext', wp_kses( $_POST['mob_datetext'], $allowed ) );
}
Also try to use <?php
instead of <?
for PHP opening.