How to handle database connection errors in PHP?

PHP is a scripting language widely used in Web development. It can interact with databases to access and process data. In the process of using PHP to connect to the database, you may encounter some connection errors, which will cause us to be unable to operate the database normally. Next, we'll discuss how to handle these database connection errors and provide some concrete code examples.

In PHP, we mainly use the two extensions mysqli and PDO to connect to the database. Whether using mysqli or PDO, there are some common connection errors, such as connection timeout, failure to connect to the server, etc. Below, we'll cover how to handle these connection errors in two parts.

1. Use mysqli extension to connect to the database

When using the mysqli extension to connect to the database, we can handle connection errors by catching exceptions. First, we need to create a mysqli object and set some connection parameters as follows:

$servername = "localhost";
$username = "root";
$password = "";
$dbname = "myDB";

try {
    // 创建mysqli对象
    $conn = new mysqli($servername, $username, $password, $dbname);
    
    // 设置连接超时时间为10秒
    $conn->options(MYSQLI_OPT_CONNECT_TIMEOUT, 10);
    
    // 设置字符集为UTF-8
    $conn->set_charset("utf8");
    
    // 其他数据库操作...
} catch(mysqli_sql_exception $e) {
    // 捕获连接异常
    echo "连接错误：" . $e->getMessage();
}

In the above code, we use the try-catch statement block to catch the mysqli_sql_exception exception. If a connection error occurs, an exception will be thrown, and we can get the specific error message through $e->getMessage().

2. Use PDO extension to connect to the database

When using PDO extension to connect to the database, we can also handle connection errors by catching exceptions. First, we need to create a PDO object and set some connection parameters, as shown below:

$servername = "localhost";
$username = "root";
$password = "";
$dbname = "myDB";

try {
    // 创建PDO对象
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    
    // 设置连接超时时间为10秒
    $conn->setAttribute(PDO::ATTR_TIMEOUT, 10);
    
    // 设置字符集为UTF-8
    $conn->exec("set names utf8");
    
    // 其他数据库操作...
} catch(PDOException $e) {
    // 捕获连接异常
    echo "连接错误：" . $e->getMessage();
}

In the above code, we also use the try-catch statement block to catch the PDOException exception. If a connection error occurs, an exception will be thrown, and we can get the specific error message through $e->getMessage().

In addition to catching connection exceptions, we can also use the getError() method to obtain the last error information. For example, we can get the last error message of the mysqli extension through $conn->getError().

In summary, when using PHP to connect to the database, we can handle connection errors by catching exceptions. Connection errors can be handled in a similar way whether using the mysqli extension or the PDO extension. By properly handling these connection errors, we can better improve the robustness and stability of our applications.

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