What best practices should be followed when integrating PHP functions within HTML code for form validation?

When integrating PHP functions within HTML code for form validation, it is important to ensure that the PHP code is properly embedded within the HTML form tags. This can be done by using PHP opening and closing tags within the form elements to execute validation functions. Additionally, error messages should be displayed within the HTML code to provide feedback to users. 

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Validate form data
    $name = $_POST['name'];
    $email = $_POST['email'];
    
    if (empty($name)) {
        $name_error = "Name is required";
    }
    
    if (empty($email)) {
        $email_error = "Email is required";
    }
}
?>

<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>">
    <input type="text" name="name" value="<?php echo isset($name) ? $name : ''; ?>">
    <span><?php echo isset($name_error) ? $name_error : ''; ?></span>
    
    <input type="email" name="email" value="<?php echo isset($email) ? $email : ''; ?>">
    <span><?php echo isset($email_error) ? $email_error : ''; ?></span>
    
    <input type="submit" value="Submit">
</form>

Keywords

PHP HTML form validation integration functions

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