<?php

$dns = 'mysql:dbname=mysql;host=localhost';
$db_user = 'root';
$db_password = 'admin';

$db_handler = new PDO($dns, $db_user, $db_password);
$statment = $db_handler->query('SHOW DATABASES');
$dbs = $statment->fetchAll();

$exclude_dbs = [
    'information_schema',
    'mysql',
    'performance_schema',
    'phpmyadmin',
];

$stack = [];

foreach($dbs as $db) {
    if ( ! in_array($db['Database'], $exclude_dbs)) {
        $pwd = randomPassword();
        $db_handler->query(
          'CREATE USER \''.
          $db['Database'].
          '\'@\'localhost\' IDENTIFIED BY \''.
          $pwd.'\'');
        print("\nUser {$db['Database']} created with password '{$pwd}'.");
        $db_handler->query(
          'GRANT ALL PRIVILEGES ON '.
          $db['Database'].
          '.* TO \''.
          $db['Database'].
          '\'@\'localhost\'');
        print("\nAll privileges granted for '{$db['Database']}'.*.\n\n");
        $stack[] = [
            'username' => $db['Database'],
            'password' => $pwd,
        ];
    }
}

$db_handler->query('FLUSH PRIVILEGES');
print("Privileges flushed. Finish!\n");

file_put_contents('user_password.json', json_encode($stack));
print("Saved to 'user_password.json' file.\n\nDone.\n\n");

function randomPassword() {
    $alphabet = "abcdefghijklmnopqrstuwxyzABCDEFGHIJKLMNOPQRSTUWXYZ0123456789";
    $pass = array(); //remember to declare $pass as an array
    $alphaLength = strlen($alphabet) - 1; //put the length -1 in cache
    for ($i = 0; $i < 8; $i++) {
        $n = rand(0, $alphaLength);
        $pass[] = $alphabet[$n];
    }
    return implode($pass); //turn the array into a string
}