If You have no access to the server or htaccess file, here is the bulk PHP redirect generator to make fastest possible redirects in this situation. It generates header location rules for exact page to page redirection based on simple "if" conditions and some regular expressions syntax. Please, read notes at the bottom.
Copy and paste columns of old and new urls, for example from Google docs or Excel, into first field. Push "Generate" button. Copy 301 redirect code into your PHP application. Learn more about usage of PHP header function for 301 and other redirects here.
If you need fast 301 redirects, but can't access your server, you may use PHP side redirects to do 301 page redirection. It is still good for SEO and other purposes.
The faster the better. So the earlier the better. Place your code at the begging of the enter point php file of your application. In many cases, it can be index.php file.
Many CMS systems like WordPress can rewrite enter point file on update. So, create some file, for example 301-redirects.php, and place your redirect code in it. Include this file in your enter point file. For example, add such a line at the beginning include '301-redirects.php';