03 Variables and Types

Goal

Understand PHP's scalar types, variable syntax, and how type coercion works — the thing that trips up developers coming from stricter languages most often.

Prerequisites

• Hello World

Variables

Every variable starts with $. No declaration keyword, no type annotation required:

<?php

$name = "Mei";
$age = 29;
$price = 9.99;
$active = true;

Scalar Types

Type	Example	Notes
string	"hello" or 'hello'	double quotes interpolate $variables, single quotes don't
int	42	platform-dependent size, typically 64-bit
float	9.99	also called double
bool	true / false
null	null	absence of a value

Type Coercion — Read This Twice

PHP is dynamically typed and, by default, loosely typed: an int and a numeric string can compare equal with ==.

<?php

var_dump(0 == "abc");   // false as of PHP 8 (was true pre-8 — a real historical footgun)
var_dump("1" == "01");  // true  — both parse to the number 1
var_dump("10" == "1e1"); // true — both parse to the number 10
var_dump(100 == "1e2"); // true — both parse to the number 100

The == operator's rules changed materially in PHP 8 to make comparisons like the first one safer. Where it matters, use === (identical — same type AND same value) instead of == (equal — coerces first):

<?php

var_dump(0 === "abc"); // false — different types, no coercion attempted

Default to ===. Reach for == only when you specifically want coercion.

Type Declarations (Optional)

Since PHP 7, you can declare types on function parameters and return values — this is what "gradual typing" means (mentioned in the PHP Language track):

<?php

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

More on this once functions are introduced.

Checkpoint

php -a

This opens PHP's interactive shell (REPL). Try:

php > var_dump("5" == "05");
bool(true)
php > var_dump("5" === "05");
bool(false)

Type exit to leave.

Next

Continue to 04 Control Flow.