PHP for Beginners: The Basics

Functions and Forms

2 min read Last updated 44 minutes ago

Functions bundle logic into reusable pieces, and forms are how PHP collects data.

Defining functions

php

<?php
function greet(string $name): string
{
    return "Hello, {$name}!";
}

echo greet("TutsFx"); // Hello, TutsFx!

PHP 8 supports type hints on parameters and return types.

Default values

php

<?php
function applyDiscount(float $price, float $percent = 10): float
{
    return $price * (1 - $percent / 100);
}

echo applyDiscount(100);      // 90
echo applyDiscount(100, 50);  // 50

Handling a form POST

html

<form method="post" action="subscribe.php">
    <label for="email">Email</label>
    <input type="email" name="email" id="email" required>
    <button type="submit">Subscribe</button>
</form>

php

<?php
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $email = filter_var($_POST['email'] ?? '', FILTER_VALIDATE_EMAIL);

    if ($email === false) {
        echo "Please provide a valid email address.";
    } else {
        echo "Thanks! We saved {$email}.";
    }
}

✓

Validate, don't trust

Always filter_var or use a validation library. Storing raw POST data is how sites get hacked.

Calling functions in templates

php

<?php
function total(array $cart): float
{
    $sum = 0;
    foreach ($cart as $item) {
        $sum += $item['price'] * $item['qty'];
    }
    return $sum;
}
?>

<p>Cart total: $<?= total($cart) ?></p>

<?= ?> is shorthand for <?php echo ?> — keep it for short outputs.

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