How to connect to MySQL using PHP

How to connect to MySQL using PHP: 1. Use PHP’s mysql_connect statement to connect; 2. Use PHP’s MySQLi statement to connect; 3. Use the PDO method to connect.

The operating environment of this article: Windows 7 system, Dell G3 computer, PHP version 7.1.

We can use PHP's mysql_connect statement, MySQLi statement or PDO to connect to MySQL. Here is a brief introduction in this article. I hope it will be helpful to everyone.

Before we can access the data in the MySQL database, we need to be able to connect to the MySQL server. Let's take a look at how to connect to MySQL.

Use PHP's mysql_connect statement

PHP provides the mysql_connect function to open a database connection. Let's take a look at how to implement it:

Step 1. Use the following PHP code to connect to MySQL and select the database.

<?php
    $con = mysql_connect（&#39;localhost&#39;，&#39; username &#39;，&#39; password &#39;）;
    $db_selected = mysql_select_db("dbname", $con);
?>

Note: You need to replace username and password with your own MySQL account name and password; and change dbname to your own defined database name.

Step 2. After connecting to MySQL and selecting a database, you can run SQL queries and perform other operations. For example, the following PHP code runs a SQL query that extracts the name field from the employees table and stores the result in the $result variable:

<?php
    $result = mysqli_query($db_selected,&#39;SELECT name FROM employees&#39;);
?>

MySQLi statement using PHP

Method 1, MySQLi object-oriented

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

Method 2, MySQLi program

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB"
// 创建连接
$conn = mysqli_connect($servername, $username, $password,$dbname);
// 检查连接
if (!$conn) {
    die("连接失败: " . mysqli_connect_error());
}
echo "连接成功";
?>

Using PDO

<?php
$servername = "localhost";
$username = "username";
$password = "password";
try {
    $conn = new PDO("mysql:host=$servername;dbname=myDB", $username, $password);
    // 将PDO错误模式设置为异常
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    echo "连接成功"; 
}
catch(PDOException $e){
    echo "连接失败:".$e->getMessage();
}
?>

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