Redirect authors from upload.php url to Home page in Multisite

Question

I would like to redirect authors when they visit the URL mynetwork.com/OWNBLOG/wp-admin/upload.php to another page. How can I do that?

I tried this code but i received this error :

"Warning: Cannot modify header information - headers already sent by (output started at /home/content/59/104129/html/wp-admin/includes/template.php:1642) in /home/content/59/10412659/html/wp-includes/pluggable.php on line 876" :

add_action( 'admin_head-upload.php', 'redirect_media_library_wpse_93626' );

function redirect_media_library_wpse_93626()
{
    // Stop if not Multisite
    if( !is_multisite() )
        return;

    // Stop if is main site
    if( is_main_blog() )
        return;

    // Stop if is administrator
    if( current_user_can( 'add_users' ) )
        return;

    // Finally, redirect
    // wp_redirect( site_url( 'personal-page' ) ); // http://subsite.example.com/personal-page
    // wp_redirect( 'http://example.com' );
    wp_redirect( admin_url() ); // http://subsite.example.com/wp-admin
    exit();
}

Answer 1

If I understand you, he hook you want (WordPress 3.5.1) is load-upload.php.

Proof of concept:

function t_wpse_94284() {
  wp_redirect(home_url()); 
  exit;
}
add_action('load-upload.php','t_wpse_94284');

That hook should fire only on /wp-admin/upload.php and, though I haven't tested it, I think that your function should work just fine as it is.

Answer 2

Unfortunately, admin_head-{pluginname} runs after things have already been outputted to the page, so you can't do a redirect there. You need to do it sooner.

View load order here: http://codex.wordpress.org/Plugin_API/Action_Reference#Actions_Run_During_an_Admin_Page_Request

You could plugin to "admin_init" instead and then just manually test for the page:

add_action( 'admin_init', 'redirect_media_library_wpse_93626' );
function redirect_media_library_wpse_93626()
{
    // Add this extra test to make sure you are on the right page.
    if ( $GLOBALS['pagenow'] != 'upload.php' ) return;

    // Stop if not Multisite
    if ( !is_multisite() ) return;

    // Stop if is main site
    if ( is_main_blog() ) return;

    // Stop if is administrator
    if ( current_user_can( 'add_users' ) ) return;

    // Finally, redirect
    // wp_redirect( site_url( 'personal-page' ) ); // http://subsite.example.com/personal-page
    // wp_redirect( 'http://example.com' );
    wp_redirect( admin_url() ); // http://subsite.example.com/wp-admin
    exit();
}