I have an existing linux server, with PHP already installed. I just need to add in the php_ldap module. I do not have root/sudo access (no yum/apt-get), what is the best way to get it installed?
Unfortunately there is none. Even if you get sources and compile it, you will still need to modify apache configuration to get it loaded. I suggest to talk to the admin of the server.
I think it cannot be done without root privilege. If you cannot talk to your client you can look for a php library replacement instead. For example there is a JSON script replaceing the JSON extension.
He didn't said that he use apache. Theoretically, if the sources of web-server and php is compiled as the user running the web-server, that should works.