3v4l.org

run code in 300+ PHP versions simultaneously
<?php function siteURL() { return "http://example.com/dir/"; } define('SITE_URL', siteURL()); //returns http://example.com/dir/ define('CKEDITOR', SITE_URL.'plugins/ckeditor/ckeditor.js'); // ignore the above code is just to emulate your code echo str_replace(SITE_URL,'',CKEDITOR);
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.24 - 5.5.35, 5.6.8 - 5.6.21, 7.0.0 - 7.0.20, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.29, 8.2.0 - 8.2.20, 8.3.0 - 8.3.8
plugins/ckeditor/ckeditor.js

preferences:
265.46 ms | 406 KiB | 362 Q