Site keeps redirecting to core/install.php

Question

I keep having this problem of drupal redirecting to core/install.php as shown below:

I already set the max_allowed_packet to 64MB on AWS RDS. I am not sure what else I am missing. Please help

The error in the logs is:

Fatal error: Cannot redeclare _drupal_shutdown_function_handle_exception() (previously declared in /var/www/html/web/core/includes/bootstrap.inc:1066) in /var/www/html/vendor/drupal/core/includes/bootstrap.inc on line 1066

and the following is my composer.json

{
  "name": "xxx/yyy",
  "description": "zzz",
  "type": "project",
  "license": "GPL-2.0-or-later",
  "authors": [
    {
      "name": "QQQ EEE",
      "role": "Developer"
    }
  ],
  "repositories": [
    {
      "type": "composer",
      "url": "https://packages.drupal.org/8"
    }
  ],
  "require": {
    "php": ">=5.6",
    "aws/aws-sdk-php": "^3.108",
    "composer/installers": "^1.2",
    "cweagans/composer-patches": "^1.6.5",
    "drupal-composer/drupal-scaffold": "^2.5",
    "drupal/console": "^1.0.2",
    "drupal/core": "^8.7.0",
    "drupal/ldap": "^3.0@beta",
    "drupal/redis": "^1.1",
    "drupal/s3fs": "^3.0",
    "drush/drush": "^9.0.0",
    "predis/predis": "^1.1",
    "vlucas/phpdotenv": "^2.4",
    "webflo/drupal-finder": "^1.0.0",
    "webmozart/path-util": "^2.3",
    "zaporylie/composer-drupal-optimizations": "^1.0"
  },
  "require-dev": {
    "webflo/drupal-core-require-dev": "^8.7.0"
  },
  "conflict": {
    "drupal/drupal": "*"
  },
  "minimum-stability": "dev",
  "prefer-stable": true,
  "config": {
    "sort-packages": true
  },
  "autoload": {
    "classmap": [
      "scripts/composer/ScriptHandler.php"
    ],
    "files": ["load.environment.php"]
  },
  "scripts": {
    "pre-install-cmd": [
      "DrupalProject\\composer\\ScriptHandler::checkComposerVersion"
    ],
    "pre-update-cmd": [
      "DrupalProject\\composer\\ScriptHandler::checkComposerVersion"
    ],
    "post-install-cmd": [
      "DrupalProject\\composer\\ScriptHandler::createRequiredFiles"
    ],
    "post-update-cmd": [
      "DrupalProject\\composer\\ScriptHandler::createRequiredFiles"
    ]
  },
  "extra": {
    "composer-exit-on-patch-failure": true,
    "patchLevel": {
      "drupal/core": "-p2"
    },
    "installer-paths": {
      "web/core": ["type:drupal-core"],
      "web/libraries/{$name}": ["type:drupal-library"],
      "web/modules/contrib/{$name}": ["type:drupal-module"],
      "web/profiles/contrib/{$name}": ["type:drupal-profile"],
      "web/themes/contrib/{$name}": ["type:drupal-theme"],
      "drush/Commands/{$name}": ["type:drupal-drush"]
    },
    "drupal-scaffold": {
      "initial": {
        ".editorconfig": "../.editorconfig",
        ".gitattributes": "../.gitattributes"
      }
    }
  }
}

Answer 1

You've got a problem with your installation. You have two copies of core, as can be seen from the two paths in the error message:

/var/www/html/web/core/includes/bootstrap.inc

/var/www/html/vendor/drupal/core/includes/bootstrap.inc

You should not have a copy of core in your vendor directory. That needs to be removed, though it may also break your site. Make sure to clear the registry drush cr or equivalent after removing that directory.