Allow multiple post types to use same add_meta_box call (Pass an array for the $page arg)

[idealien]

The $page parameter of add_meta_box ​http://codex.wordpress.org/Function_Reference/add_meta_box currently only accepts a string to "The type of Write screen on which to show the edit screen section ('post', 'page', or 'link')".

In discussing best way to allow for multiple post types to use the same meta box with 3.0 (beta), scribu indicated that currently one would have to call add_meta_box twice.

scibu: come to think of it, you should be able to pass an array for the $page arg

[nacin]

Should be simple enough to check if $page is an array, and if so, call add_meta_box again with the same parameters otherwise.

Related: #13937

[markjaquith]

Just leverage the variables passed to the do_meta_boxes callback.

function your_callback( $page, $context ) {
    if ( in_array( $page,  array( 'post', 'page' ) ) && 'normal' == $context )
        add_meta_box( 'your-id', 'Title', 'your_box_callback', $page, $context, 'high' );
}

add_action( 'do_meta_boxes', 'your_callback', 10, 2 );