4vxZQV6k

1<?php
2
3namespace ACompany\AnAppName\Dao\PdoImpl;
4
5use PDO;
6use Exception;
7use PDOException;
8/**
9 * UPDATE: I'm leaving the author's original comments, but this has been updated to better represent a singleton PDO
10 * connection. The author's original code would create a new connection on each call to getConnection.
11 *
12 * The other thing it did was set all of these methods and properties to 'protected', but then called 'self' - if you
13 * want this class to be extendable then you should use 'static' due to PHP's 'Late static binding'.
14 *
15 * Also I'm using the PSR-2 style guidelines.
16 *
17 * While I'm NOT condoning this as a 'best practice' I thought I would at least correct the misconception that this was
18 * creating a single connection.
19 *
20 * Usage now is:
21 * $pdo = PDOConnection::instance('dsn', 'username', 'password'); // first call only.
22 * $connection = $pdo->getConnection();
23 *
24 * Once you know the instance has been created you can just call: $pdo = PDOConnection::instance();
25 *
26 **** ORIGINAL COMMENTS ****
27 *
28 * PDOConnection is a singleton implementation.
29 * getConnection() returning an instance of PDO connection.
30 *
31 * <code>
32 * Example usage:
33 *
34 * $pdo = PDOConnection::instance();
35 * $conn = $pdo->getConnection( 'dsn', 'username', 'password' );
36 *
37 * $results = $conn->query("SELECT * FROM Table");
38 *
39 * </code>
40 *
41 * @author rmurray
42 */
43class PDOConnection
44{
45    protected static $instance = null;
46
47    /** @var PDO */
48    protected $connection = null;
49    /**
50     * PDOConnection constructor.
51     * @param $dsn
52     * @param $username
53     * @param $password
54     * @throws PDOException
55     * @throws Exception
56     */
57    protected function __construct($dsn, $username, $password)
58    {
59        try {
60            $this->connection = new PDO($dsn, $username, $password);
61            //Set common attributes
62            $this->connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
63        } catch (PDOException $e) {
64            //TODO: flag to disable errors?
65            throw $e;
66        } catch(Exception $e) {
67            //TODO: flag to disable errors?
68            throw $e;
69        }
70    }
71    
72    /**
73     * Get the current active instance if one exists, otherwise create a new instance.
74     *
75     * @param string|null $dsn
76     * @param string|null $username
77     * @param string|null $password
78     * @throws PDOException
79     * @throws Exception
80     * @return PDOConnection
81     */
82    public static function instance($dsn = null, $username = null, $password = null) {
83        if (!isset(static::$instance)) {
84            if (!isset($dsn) || !isset($username) || !isset($password)) {
85                throw new Exception('No instance exists. You must provide the dsn, username, and password.');
86            }
87
88            static::$instance = new static($dsn, $username, $password);
89        }
90
91        return static::$instance;
92    }
93    
94    /**
95     * Return a PDO connection
96     *
97     * @return PDO
98     */
99    public function getConnection()
100    {
101        return $this->connection;
102    }
103    /** PHP seems to need these stubbed to ensure true singleton **/
104    private function __clone() {}
105    private function __wakeup() {}
106}