How can PHP developers handle form validation and error messaging without relying on Ajax?

When handling form validation and error messaging without relying on Ajax, PHP developers can utilize server-side validation techniques and display error messages directly on the page upon form submission. This can be achieved by checking form input data in the PHP script, setting error messages in variables, and then echoing these messages within the HTML form. 

<?php
$errors = array();

if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Validate form inputs
    if (empty($_POST["username"])) {
        $errors[] = "Username is required";
    }

    if (empty($_POST["password"])) {
        $errors[] = "Password is required";
    }

    // Display error messages
    if (!empty($errors)) {
        foreach ($errors as $error) {
            echo "<p style='color: red;'>$error</p>";
        }
    }
}
?>

<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>">
    <input type="text" name="username" placeholder="Username">
    <input type="password" name="password" placeholder="Password">
    <button type="submit">Submit</button>
</form>

Keywords

PHP form validation error messaging server-side validation client-side validation

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