Change Permalink Based on Custom Field

gistfile1.php

add_action('init', 'tdd_add_rewrite_rules');
 
function tdd_add_rewrite_rules()
 
{
 
// Register custom rewrite rules
 
global $wp_rewrite;
$wp_rewrite->add_rewrite_tag('%your_post_type%', '([^/]+)', 'your_post_type=');
$wp_rewrite->add_rewrite_tag('%your_custom_field%', '([^/]+)', 'your_custom_field=');
 
$wp_rewrite->add_permastruct('your_post_type', '/%your_custom_field%/%your_post_type%', false);
 
}

add_filter('post_type_link', 'tdd_permalinks', 10, 3);
 
function tdd_permalinks($permalink, $post, $leavename)
 
{
 
$no_data = 'no-speciality';
 
$post_id = $post->ID;
 
if($post->post_type != 'your_post_type' || empty($permalink) || in_array($post->post_status, array('draft', 'pending', 'auto-draft')))
 
return $permalink;
 
$var1 = get_post_meta($post_id, 'your_custom_field', true);
 
$var1 = sanitize_title($var1);
 
if(!$var1) { $var1 = $no_data; }
 
$permalink = str_replace('%your_custom_field%', $var1, $permalink);
 
return $permalink;
 
}

• Add to functions.php inside a WordPress theme
• Change all instances of your_post_type with the custom post type you want to use.
• Change all instances of your_custom_field with the field name you want to use.