How to handle form validation errors in PHP?

How to handle form validation errors in PHP?

When developing web applications, form validation is a very important step. By validating form data, you can ensure that the data entered by the user conforms to the expected format and requirements, ensuring the accuracy and security of the program. When users submit form data, some errors may occur, such as missing required fields, incorrect field formats, etc. At this time, we need to catch and handle these errors in a timely manner.

The following are some common form validation error handling methods and sample codes:

1. Display error message

When form validation fails, the most common The method is to display the error message to the user to let the user know what went wrong. You can use HTML and CSS to beautify the display of error messages.

Sample code:

// 表单验证
if ($username == '') {
    $errors['username'] = '用户名不能为空';
}
if ($password == '') {
    $errors['password'] = '密码不能为空';
}

// 显示错误信息
if (!empty($errors)) {
    echo '<ul>';
    foreach ($errors as $error) {
        echo '<li>' . $error . '</li>';
    }
    echo '</ul>';
}

2. Jump to the original form page

When a form validation error occurs, the user can be redirected to the original form page , to prevent users from refilling the form. At the same time, the error information can also be passed to the original form page during redirection to facilitate users to view the error information.

Sample code:

// 表单验证
if ($username == '') {
    $errors['username'] = '用户名不能为空';
}
if ($password == '') {
    $errors['password'] = '密码不能为空';
}

// 处理表单提交
if (!empty($errors)) {
    // 将错误信息传递给原始表单页面
    session_start();
    $_SESSION['errors'] = $errors;
    header('Location: form.php'); // 重定向到原始表单页面
    exit();
}

// 原始表单页面
session_start();
if (isset($_SESSION['errors'])) {
    echo '<ul>';
    foreach ($_SESSION['errors'] as $error) {
        echo '<li>' . $error . '</li>';
    }
    echo '</ul>';
    unset($_SESSION['errors']);
}

3. Form data retention

When a form validation error occurs, in order to facilitate the user to find and correct the error, the filled-in data can be saved The form data remains in the form.

Sample code:

// 表单验证
if ($username == '') {
    $errors['username'] = '用户名不能为空';
}
if ($password == '') {
    $errors['password'] = '密码不能为空';
}

// 处理表单提交
if (!empty($errors)) {
    // 将表单数据传递给原始表单页面
    session_start();
    $_SESSION['form_data'] = $_POST;
    $_SESSION['errors'] = $errors;
    header('Location: form.php'); // 重定向到原始表单页面
    exit();
}

// 原始表单页面
session_start();
if (isset($_SESSION['form_data'])) {
    $form_data = $_SESSION['form_data'];
    unset($_SESSION['form_data']);
}
if (isset($_SESSION['errors'])) {
    echo '<ul>';
    foreach ($_SESSION['errors'] as $error) {
        echo '<li>' . $error . '</li>';
    }
    echo '</ul>';
    unset($_SESSION['errors']);
}

// 在表单元素中使用保持的表单数据
<input type="text" name="username" value="<?php echo isset($form_data['username']) ? $form_data['username'] : ''; ?>">

The above are some common methods and sample codes for handling form validation errors. Appropriate modifications and optimizations can be made according to actual needs and framework characteristics. The purpose of form validation is to ensure the accuracy and security of data, so when handling form validation errors, the comprehensive factors of user experience and data integrity should be taken into consideration.

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