检查php脚本的php版本兼容性

I have a php script. I want to check the php version compatibility that each function of this script has. For example the script has the hash() function. If we look at php.net site it says that this function was added (PHP 5 >= 5.1.2, PECL hash >= 1.1). So assuming that this script has only this function we say that it is compatible with php 5.1.2 and onwards. Is there any software tool that can scan the script and tell you the changelog of every function and possibly gives you the lowest possible score e.g. (php version 4.3 and on)? It is a bit tedious to check manually every function in the script. Thank you in advanceI have a php script. I want to check the php ve