PHP connection MySQL related knowledge and operations

How to connect through phpmysql database, this chapter will explain the database connection in detail.

Connecting to MySQL

Before we access the MySQL database, we need to connect to the database server first:

Instance (MySQLi - Object-oriented)

<?php$servername = "localhost";$username = "username";$password = "password"; 
// 创建连接$conn = new mysqli($servername, $username, $password); 
// 检测连接if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);} echo "连接成功";?>

Note that $connect_error in the above object-oriented example was added in PHP 5.2.9 and 5.3.0. If you need to be compatible with earlier versions, please use the following code replacement:

// 检测连接
if (mysqli_connect_error()) {
    die("数据库连接失败: " . mysqli_connect_error());
}

Instance (MySQLi - process-oriented)

<?php$servername = "localhost";$username = "username";$password = "password"; 
// 创建连接$conn = mysqli_connect($servername, $username, $password); 
// 检测连接if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());}echo "连接成功";?>

Instance (PDO)

<?php$servername = "localhost";$username = "username";$password = "password"; 
try {
    $conn = new PDO("mysql:host=$servername;dbname=myDB", $username, $password);    echo "连接成功"; 
}catch(PDOException $e){
    echo $e->getMessage();}?>

Note that In the above PDO example, we have specified the database (myDB). PDO needs to set the database name during the connection process. If not specified, an exception will be thrown.

$conn->close();

mysqli_close($conn);

$conn = null;

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