An Introduction to the WP_Error Class

WP_Error class for WordPress: elegant error handling mechanism

WordPress's WP_Error class provides a simple and powerful error handling mechanism for managing and modifying errors in applications. It is easy to integrate into your application, effectively handles errors returned by WordPress core functions, and creates custom error messages to improve the user experience. In addition, practical functions such as is_wp_error can check whether the variable or function return value is an instance of WP_Error, thereby debugging problems efficiently.

No matter how skillful and meticulous your code is written, errors cannot be avoided in any development process. As a WordPress developer, it is your responsibility to make sure all code errors are handled correctly without affecting the end user. WordPress comes with a basic error handling class WP_Error, which can be integrated into your code for basic error handling.

This tutorial will explore the basic structure and working principles of WP_Error classes, and most importantly, we will introduce how to integrate WP_Error classes in your application.

WP_Error Detailed explanation of the category

WP_Error The class has a simple structure but powerful function, which is enough to be used as an error handling mechanism for plug-ins. Its source code is located in the wp-includes/class-wp-error.php file. Let's take a look at its properties and methods.

Properties

WP_Error There are only two private attributes: $errors and $error_data. $errors is used to store related error messages, while $error_data is optionally used to store relevant data you want to access later. WP_Error Use simple key-value pairs to store related errors and data into an object, so the keys defined in WP_Error must be unique to avoid overwriting previously defined keys.

Method

WP_Error Provides several ways to modify the two properties it contains. Let's look at a few:

• get_error_codes(): Returns all available error codes for a specific WP_Error instance. If only the first error code is needed, another separate function is available. get_error_code()
• : If get_error_messages( $code ) is not provided, the function will simply return all messages stored in the specific $code instance. Similarly, if you only need to return a message with a specific error code, just use WP_Error. get_error_message( $code )
• : This function is especially useful when you want to modify errors stored in instantiated add( $code, $message, $data ) objects. Note that even if WP_Error and $message are not required, the $data variables will still be filled. $errors
• : If you only want to modify the add_data( $data, $code) property, you can use this function. Note that the $error_data parameter is in the second position, opposite to the $code method. If add is not provided, the error data will be added to the first error code. $code
• : This is a new method recently added in WordPress 4.1, which removes all error messages and data associated with a specific key. remove( $code )

Function

How do you know if the specific variable or data returned by a function is an instance of

? You can check using a utility function WP_Error which returns true or false based on the given variable. is_wp_error()

• : Return true if is_wp_error( $thing ) is an instance of $thing, otherwise return false. WP_Error

Implement in your application

WP_Error

Just just understand how

works internally, you also need to learn how to implement it well in your own application. Let's take a few examples to better understand how it works. WP_Error

Processing errors returned by WordPress core function

WordPress provides many practical functions that can be used to speed up our development process. Most functions are also equipped with basic error handling functions that we can use.

For example,

is a very useful function that we can use to make a remote POST request to a specific URL. However, we cannot expect the remote URL to be always accessible, or our requests are always successful. We know from the manual page that this function will return wp_remote_post when it fails. This knowledge will help us to correctly implement error handling in our application. WP_Error

Please see this code:

// 向远程 URL $url 发出请求
$response = wp_remote_post( $url, array(
    'timeout' => 30,
    'body' => array( 'foo' => 'bar' )
    )
);

if ( is_wp_error( $response ) ) {
   echo 'ERROR: ' . $response->get_error_message();
} else {
    // 执行某些操作
}

As you can see, we are performing a remote POST request to

. However, instead of simply getting the $url data as is, we do some checks using the convenient $response function introduced earlier. If everything works, we can continue to do what we want to do with is_wp_error. $response

Return custom error in your application

Suppose you have a custom function that handles the submission of a contact form, named handle_form_submission. Suppose we set up a custom form somewhere, let's see how we can improve the function by implementing our own error handling capabilities.

// 向远程 URL $url 发出请求
$response = wp_remote_post( $url, array(
    'timeout' => 30,
    'body' => array( 'foo' => 'bar' )
    )
);

if ( is_wp_error( $response ) ) {
   echo 'ERROR: ' . $response->get_error_message();
} else {
    // 执行某些操作
}

Of course, you also need to implement your own cleaning and verification in these functions, but this is not within the scope of this tutorial. Now, knowing that we correctly return the WP_Error instance when we are error-based, we can use it to provide more meaningful error messages to the end user.

Suppose there is a specific part in your application that displays form submission errors, you can do this:

function handle_form_submission() {
    // 在此处执行你的验证、nonce 等操作

    // 实例化 WP_Error 对象
    $error = new WP_Error();

    // 确保用户提供名字
    if ( empty( $_POST['first_name'] ) ) {
        $error->add( 'empty', 'First name is required' );
    }

    // 也需要姓氏
    if ( empty( $_POST['last_name'] ) ) {
        $error->add( 'empty', 'Last name is required' );
    }

    // 检查电子邮件地址
    if ( empty( $_POST['email'] ) ) {
        $error->add( 'empty', 'Email is required' );
    } elseif ( ! is_email( $_POST['email'] ) ) {
        $error->add( 'invalid', 'Email address must be valid' );
    }

    // 最后，检查消息
    if ( empty( $_POST['message'] ) ) {
        $error->add( 'empty', 'Your message is required' );
    }

    // 发送结果
    if ( empty( $error->get_error_codes() ) ) {
        return true; // 没有错误
    }

    // 有错误
    return $error;
}

Summary

Striving to excel in software development also means knowing what to do when your code cannot do what it should do, and making sure your application can handle it gracefully.

For WordPress, using the included WP_Error class provides a fairly simple but powerful error handling implementation that you can integrate into your application.

(The external references and FAQ sections in the original text are omitted here because they are direct copies of the original text and do not meet the requirements of pseudo-originality.)

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