in MACOSX11, the pre-installed version of PHP is 5.5. I installed PHP7, with brew myself. When using composer install, the PHP is required to be no less than 5.6. what should I do? 
 first of all, mac os is not as simple as linux to delete / usr/bin/php, and then build a soft link to the new version of PHP. 
 the core services pre-installed in the MAC OS system cannot be modified by root users. Unless the Rootless mechanism is turned off. But I don"t want to do that. 
 is there any other way to ask the god? 


