Integration of PHP and database error handling

During the development process, database error handling is a very important part. Because we cannot guarantee that every data is correct and complete, some unexpected errors may occur during the process of reading and writing the database. Therefore, developers must pay attention to handling these errors reasonably in the program to ensure the robustness of the program.

PHP is a very commonly used backend programming language. One of its advantages is that it is very convenient to integrate with the database. For database error handling, some of PHP's built-in functions, such as PDO, mysqli, mysql, etc., have good handling methods. Below, we take PDO as an example to introduce the integration of PHP and database error handling in detail.

PHP PDO (PDO PHP Data Object) is a lightweight database access library that supports a variety of data access, including MySQL, PostgreSQL, Oracle, etc. When using PDO to connect to the database, we can control PDO's error handling method by setting the errorMode attribute. If we need to handle PDO errors, we can set the errorMode attribute of the PDO object to PDO::ERRMODE_EXCEPTION or PDO::ERRMODE_WARNING.

In PDO::ERRMODE_EXCEPTION mode, PDO will throw an exception when an error is detected. This exception contains error information, error code and other detailed information. We can handle these exceptions later. The sample code is as follows:

try {  
    $pdo = new PDO('mysql:host=localhost;dbname=test;charset=utf8','root','password');  
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);  //设置PDO的错误模式为异常抛出  
} catch (PDOException $e) {  
    echo 'Connection failed: '.$e->getMessage();  
}

PDO::ERRMODE_WARNING mode, PDO will not throw an exception, but will issue a warning when an error is detected. This method is suitable for some non-critical operations. We just want to remind ourselves when a warning occurs, but do not want the program execution to be suspended. The sample code is as follows:

$pdo = new PDO('mysql:host=localhost;dbname=test;charset=utf8','root','password');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_WARNING);  //设置PDO的错误模式为警告  

After setting the error mode of PDO, we can perform corresponding error handling in the program. For details on the corresponding relationship between PDO error codes, please refer to the official documentation. For example, for the SQLSTATE[HY000]: General error error, we can handle it in the program as follows:

try {
    //执行操作
} catch (PDOException $e) {
    if($e->getCode()=='HY000'){  
        //处理错误  
        echo $e->getMessage();    
    } 
}

In addition to setting the error mode, we can also get the error code and errorInfo method by calling the errorCode and errorInfo methods of the PDO object. error information to handle the error. For example:

$pdo = new PDO('mysql:host=localhost;dbname=test;charset=utf8','root','password');
$stmt = $pdo->prepare('SELECT * FROM customer');
if(!$stmt->execute()){
    $error = $pdo->errorInfo();
    echo '查询失败，错误码：'.$error[1].' 错误信息：'.$error[2];
}

In the above code, we determine whether an error has occurred by detecting whether the return value of the SQL statement is false. When an error occurs, we call PDO's errorInfo method to obtain the error information and output a prompt message to the user.

In summary, PHP PDO provides us with a convenient and simple database access method, and also provides a complete error handling method. If we make reasonable use of PDO's error handling method during development, we can greatly improve the robustness of the program.

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