Using Form to alter PHP variable [closed]

Don’t put your variables in single quotes.

This:

if(isset($submit)){
    $args = array(
        'numberposts'     => 10,
        'meta_key'        => '$filter',
        'orderby'         => 'meta_value',
        'order'           => 'DESC',
        'post_type'       => 'things',
        'post_status'     => 'publish' );
    $mystuff = get_posts( $args );
    $name = $filter ;
}

Should be this:

if(isset($submit)){
    $args = array(
        'numberposts'     => 10,
        'meta_key'        => $filter,
        'orderby'         => 'meta_value',
        'order'           => 'DESC',
        'post_type'       => 'things',
        'post_status'     => 'publish' );
    $mystuff = get_posts( $args );
    $name = $filter ;
}