Last updated: August 27, 2026.
PHP variables begin with $ and receive their type from the assigned value. Variable names are case-sensitive, so $total and $Total are different variables.
Assign and use values
<?php
$name = 'Ada';
$itemCount = 3;
$price = 12.50;
$isActive = true;
$total = $itemCount * $price;
echo "{$name}: " . number_format($total, 2);
?>Inspect and declare types
<?php
declare(strict_types=1);
function invoiceTotal(float $price, int $quantity): float
{
return $price * $quantity;
}
var_dump(invoiceTotal(14.95, 2));
?>Variable scope
A variable created inside a function is local to that function. Pass inputs as parameters and return results explicitly.
<?php
$taxRate = 0.08;
function addTax(float $subtotal, float $rate): float
{
return $subtotal * (1 + $rate);
}
echo addTax(50, $taxRate);
?>Read external input deliberately
<?php
$page = filter_input(INPUT_GET, 'page', FILTER_VALIDATE_INT);
$page = ($page !== false && $page !== null && $page > 0) ? $page : 1;
?>Superglobals such as $_GET and $_POST contain untrusted input. Validate values for their intended use and encode them when inserting them into HTML. See PHP variable basics.
