vercel.json

{
    "version": 2,
    "builds": [
      {
        "src": "public/index.php",
        "use": "@vercel/php"
      }
    ],
    "routes": [
      {
        "src": "/(.*)",
        "dest": "/public/$1"
      }
    ],
    "env": {
      "DEFAULT_DOMAIN": "${DEFAULT_DOMAIN}",
      "IS_HTTPS_ENABLED": "${IS_HTTPS_ENABLED}"
    },
    "functions": {
      "*/*.php": {
        "runtime": "@vercel/php@0.3.0"
      }
    },
    "build": {
      "env": {
        "COMPOSER_HOME": "/app/composer",
        "COMPOSER_CACHE_DIR": "/app/composer/cache"
      },
      "scripts": [
        {
          "_script" : ["mkdir", "-p", "/var/task/user/data/log"],
          "_stage" : ["ready"],
          "_optional" : true
         },
         {
          "_script" : ["mkdir", "-p", "/var/task/user/data/cache"],
          "_stage" : ["ready"],
          "_optional" : true
         },
         {
          "_script" : ["chmod", "-R", "+x", "/var/task/user/data/log"],
          "_stage" : ["ready"],
          "_optional" : true
         },
         {
          "_script" : ["chmod", "-R", "+x", "/var/task/user/data/cache"],
          "_stage" : ["ready"],
          "_optional" : true
         }
       ]
     }
  }