hook_requirements($phase)
Check installation requirements and do status reporting.
This hook has three closely related uses, determined by the $phase argument:
Checking installation requirements ($phase == 'install'). Checking update requirements ($phase == 'update'). Status reporting ($phase == 'runtime').
Note that this hook, like all others dealing with installation and updates, must reside in a module_name.install file, or it will not properly abort the installation of the module if a cri