How to force Composer to use a specific PHP-version

This week I had a situation where I was running a different PHP-version locally than on the server. The reason for that isn't relevant, but I know this happens more often than you think. In this short tutorial I'll show you how to override your local PHP-version and force Composer to use a specific PHP-version.

Force Composer to use a specific PHP-version

The fix for this is actually pretty simple. To override the Composer PHP-version, go to your composer.json file. Under the key config, you should add a new array:

 "config": {
    "optimize-autoloader": true,
    "preferred-install": "dist",
    "sort-packages": true,
    "allow-plugins": {},
+   "platform": { 
+     "php": "8.0.5" 
+   } 
 },

This will force Composer to use that specific PHP-version. It is a good idea to use SSH to go to your server and check the exact PHP-version, so that you can use that one.

The benefit of doing this is that the complete team will generate the same composer.lock files, so I'd recommend this for most (critical) apps.