WordPress: include custom CSS file if page slug matches CSS file name.

wordpres-custom-css.php

/* Check if css file of slug name exists and if it does, include stylesheet for that slug */
function check_for_css() { 
    global $post;
    $post_slug = $post->post_name;

    $filename = get_template_directory() . '/css/' . $post_slug . '.css';

    if (file_exists($filename)) {
        echo '<link rel="stylesheet" id="' . $post_slug . '-css" href="' . get_template_directory_uri() . '/css/' . $post_slug . '.css" type="text/css" media="all" />';
    }
}
add_action('wp_footer', 'check_for_css');