Author - Pawandeep Kaur Post Views - 95 views
Table Data Gateway

Explain this pattern with an example in PHP – Table Data Gateway

A design pattern called Table Data Gateway uses an object to serve as a gateway to a database table. The goal is to keep the task of retrieving items from a database apart from how those objects are actually used. As a result, modifications to the database’s object storage scheme are protected from users of the gateway.

Now, let us understand how this pattern helps with SQL operations. I am creating a database helper class based on the TDB pattern to perform basic CRUD operations.

  1. Create an AbstractTableGateway class:

    <?php
    abstract class AbstractTableGateway
    {
    protected $db;
    protected $tablename;
    protected $columns;
    protected $primary = 'id';
    public function __construct(\PDO $db)
    {
    $this->db = $db;
    }
    public function listallrecordsBySQL(string $sql, array $params): array
    {
    $stmt = $this->db->prepare($sql);
    $stmt->execute($params);
    return $stmt->fetchAll();
    }
    public function getRecordbyID($id): ?array
    {
    $ret = $this->listallrecordsBySQL("SELECT * FROM $this->tablename WHERE $this->primary=?", [$id]);
    return $ret ? reset($ret) : null;
    }
    public function updateRecordbyID(array $data, int $id): void
    {
    $this->validate($data);
    $params = [];
    $set = "";
    foreach($data as $key => $value)
    {
    $set .= "’$key’ = ?,";
    $params[] = $value;
    }
    $set = rtrim($set, ",");
    $params[] = $id;
    $sql = "UPDATE $this->tablename SET $set WHERE $this->primary=?";
    $this->db->prepare($sql)->execute($params);
    }
    public function insertData($data): int
    {
    $this->validate($data);
    $columns = "'".implode("’,’", array_keys($data))."’";
    $placeholders = str_repeat('?,', count($data) - 1) . '?';
    $sql = "INSERT INTO $this->tablename ($columns) VALUES ($placeholders)";
    $this->db->prepare($sql)->execute(array_values($data));
    return $this->db->lastInsertId();
    }
    public function delete($id)
    {
    $sql = "DELETE FROM $this->tablename WHERE $this->primary=?";
    $this->db->prepare($sql)->execute([$id]);
    }
    protected function validate($data)
    {
    $diff = array_diff(array_keys($data), $this->columns);
    if ($diff) {
    throw new \InvalidArgumentException("Unknown field(s): ". implode($diff));
    }
    }
    }

  2. Now we create a child class named as “UserTableGateway” where we first set the properties of the “AbstractTableGateway” class as below:
    <?php
    class UserTableGateway extends AbstractTableGateway {
    protected $tablename = 'users';
    protected $columns = ['name', 'email', 'password'];
    }
  3. Now, we are going to call the AbstractTableGateway class functions to perform the CRUD operations:
    <?php
    $data = [
    'name' => 'Test User',
    'email' => 'testuser@gmail.com',
    'password' => 'hashed'
    ];
    $id = $UserTableGateway->insertData($data); // Insert the record
    $user_record = $UserTableGateway->getRecordbyID($id); //Get record by ID
    print_r( json_encode($user_record));
    $UserTableGateway->update(['name' => 'Test Account'], $id); //Update the name from “Test User” to “Test Account’
    $user_record = $UserTableGateway->getRecordbyID($id); //Get record by ID
    print_r( json_encode($user_record));
    $UserTableGateway->delete($id); //Delete the “Test Account” record

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