Learn Required Fields and Basic Validation

When users submit data through a web form, you must ensure the data is complete and valid before processing it. Validation is crucial because it protects your application from missing, malformed, or malicious input. Without validation, users might submit incomplete forms, or attackers could inject harmful data.

index.php


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<?php
$name = $email = "";
$nameErr = $emailErr = "";
$success = false;

if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Check if name is empty
    if (empty($_POST["name"])) {
        $nameErr = "Name is required";
    } else {
        $name = trim($_POST["name"]);
    }

    // Check if email is empty
    if (empty($_POST["email"])) {
        $emailErr = "Email is required";
    } else {
        $email = trim($_POST["email"]);
    }

    // If no errors, process the form (for demonstration, just show success)
    if (empty($nameErr) && empty($emailErr)) {
        $success = true;
    }
}
?>

<!DOCTYPE html>
<html>
<head>
    <title>Simple PHP Form Validation</title>
</head>
<body>
    <?php if ($success): ?>
        <h2>Form submitted successfully!</h2>
        <p>Name: <?php echo htmlspecialchars($name); ?></p>
        <p>Email: <?php echo htmlspecialchars($email); ?></p>
    <?php else: ?>
        <form method="post" action="">
            <label>Name: <input type="text" name="name" value="<?php echo htmlspecialchars($name); ?>"></label>
            <span style="color:red;"><?php echo $nameErr; ?></span><br><br>

            <label>Email: <input type="text" name="email" value="<?php echo htmlspecialchars($email); ?>"></label>
            <span style="color:red;"><?php echo $emailErr; ?></span><br><br>

            <input type="submit" value="Submit">
        </form>
    <?php endif; ?>
</body>
</html>

Required fields are form inputs that must be filled out; if any required field is empty, you should prevent further processing and prompt the user to provide the missing information. PHP allows you to check form data on the server side, ensuring that even if a user disables client-side validation or sends data directly to your server, your application remains protected.

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Section 2. Chapter 4

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index.php


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<?php
$name = $email = "";
$nameErr = $emailErr = "";
$success = false;

if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Check if name is empty
    if (empty($_POST["name"])) {
        $nameErr = "Name is required";
    } else {
        $name = trim($_POST["name"]);
    }

    // Check if email is empty
    if (empty($_POST["email"])) {
        $emailErr = "Email is required";
    } else {
        $email = trim($_POST["email"]);
    }

    // If no errors, process the form (for demonstration, just show success)
    if (empty($nameErr) && empty($emailErr)) {
        $success = true;
    }
}
?>

<!DOCTYPE html>
<html>
<head>
    <title>Simple PHP Form Validation</title>
</head>
<body>
    <?php if ($success): ?>
        <h2>Form submitted successfully!</h2>
        <p>Name: <?php echo htmlspecialchars($name); ?></p>
        <p>Email: <?php echo htmlspecialchars($email); ?></p>
    <?php else: ?>
        <form method="post" action="">
            <label>Name: <input type="text" name="name" value="<?php echo htmlspecialchars($name); ?>"></label>
            <span style="color:red;"><?php echo $nameErr; ?></span><br><br>

            <label>Email: <input type="text" name="email" value="<?php echo htmlspecialchars($email); ?>"></label>
            <span style="color:red;"><?php echo $emailErr; ?></span><br><br>

            <input type="submit" value="Submit">
        </form>
    <?php endif; ?>
</body>
</html>

Everything was clear?

Thanks for your feedback!

Section 2. Chapter 4