Best practices for error handling in PHP functions

PHP is a widely used scripting language, especially in Web development, which plays a very important role. In the process of PHP development, error handling is a very important issue. Function error handling is a very important part of it. This article will introduce some best practices for PHP function error handling to help developers better face various errors that may occur while writing high-quality code.

1. Use the try/catch structure

PHP provides the try/catch structure, which is also the most basic way of handling PHP function errors. Use the try/catch structure to perform error handling when an error occurs in the code to prevent the code from crashing due to a single error.

For example, the following is a simple function that is used to connect to the database and execute a SQL query:

function run_query($query) {
    $conn = mysqli_connect("localhost", "username", "password", "database");
    if(!$conn) {
        throw new Exception("Database connection failed.");
    }
    $result = mysqli_query($conn, $query);
    if(!$result) {
        throw new Exception("Query failed: " . mysqli_error($conn));
    }
    mysqli_close($conn);
    return $result;
}

In the function, if there is an error connecting to the database or executing the query, we will throw An exception occurs. However, during the function call process, we need to use the try/catch structure to catch these exceptions and handle them accordingly:

try {
    $result = run_query("SELECT * FROM users");
} catch(Exception $e) {
    echo "Error: " . $e->getMessage();
    exit;
}
//使用$result继续代码的执行

In this way, when a problem occurs in the function, the code will not crash, but will output error message and stops script execution. This can improve the robustness of your code.

2. Use error level control

In PHP, we can use the error level to control the error handling method of the function. By passing different error levels to the error_reporting() function, we can control the behavior of the function when an error occurs. Commonly used error levels in PHP are:

• E_ERROR: Fatal error. This error will cause the code to be unable to continue executing. You need to use die(), exit() and other functions to end the script.
• E_WARNING: Warning error. This error only reminds the developer of possible problems in the code, but will not cause the code to crash. The developer needs to make modifications based on the error message.
• E_NOTICE: Pay attention to errors. This error will not affect the execution of the code, but may cause the developer to have wrong variable values ​​​​or return results. Developers are required to review the code and make modifications.

During the development of PHP code, we recommend using appropriate error levels to ensure smooth execution of the code and high-quality output.

3. Use return value and status code

When handling function errors, we can use return value and status code in two ways. By setting different return values ​​and status codes of the function, we can obtain relevant error information after the function is executed. This is a very common error handling method and is often used in MySQLi packages.

Below we can use the return value of a function to determine whether the query is successful and return relevant query results at the same time:

function get_user_info($user_id) {
    $conn = mysqli_connect("localhost", "username", "password", "database");
    if(!$conn) {
        return array(false, "Database connection failed.");
    }
    $result = mysqli_query($conn, "SELECT * FROM users WHERE user_id={$user_id}");
    if(!$result) {
        return array(false, "Query failed: " . mysqli_error($conn));
    }
    $users = array();
    while($row = mysqli_fetch_assoc($result)) {
        $users[] = $row;
    }
    mysqli_close($conn);
    return array(true, $users);
}

In this function, if the query is successful, the function will return true and Array of query results. If the query fails, the function will return false and an error message. We can then judge the return value of the function when it is called, and thus choose how to handle errors based on the execution of the function.

$user_info = get_user_info(1);
if(!$user_info[0]) {
    echo "Error: " . $user_info[1];
    exit;
}
//使用$user_info[1]继续代码的执行

Note that when using return values ​​and status codes to handle errors, you need to avoid functions returning multiple types of results. This will increase the complexity of the code and reduce the readability of the code.

4. Combined with error logging

During the code development process, we recommend that the server be equipped with an error logging system. This logging system can catch errors while the code is running and write error information to a log file. We can use PHP's built-in error_log() function to implement logging.

function logging_query($query, $filename) {
    $conn = mysqli_connect("localhost", "username", "password", "database");
    if(!$conn) {
        error_log("Database connection failed.", 0);
        return false;
    }
    $result = mysqli_query($conn, $query);
    if(!$result) {
        error_log("Query failed: " . mysqli_error($conn), 0);
        return false;
    }
    mysqli_close($conn);
    return true;
}

Still the same as the previous example, in the function, we record error information when an error occurs. This method can not only help developers locate errors, but also monitor web applications and help us discover potential problems.

Conclusion

PHP function error handling is a very important part. In the process of code development, we often encounter various errors. By using the best practices described in this article, we can handle these errors and maintain the quality of our code. Of course, there are many other error handling methods, such as using assertions and exceptions, ensuring safety in error handling, and so on. I hope this article can help PHP developers better understand the related technologies of function error handling.

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