Variables and scalar types

Variables start with $ and are loosely typed by default—PHP figures out the type from the value. PHP 7+ adds scalar type hints and PHP 8+ strengthens the type system with union types and more.

Scalar types

• string — text in single or double quotes
• int / float — numbers; watch division (10 / 4 is float 2.5)
• bool — true / false

Assignment and reassignment

$count = 0;
$count = $count + 1;
$name = 'Tuto';

Unset with unset($name) when you need to remove a variable from the current scope.

Constants

define('APP_NAME', 'Tuto'); or const APP_VERSION = '1.0'; at class/top level. Constants are not prefixed with $.

Important interview questions and answers

1. Q: Is PHP statically typed?
   A: Historically no; you can enable strict types per file with declare(strict_types=1); and use type hints for parameters and return values.
2. Q: vs ===?
   A: == compares with type juggling; === compares value and type—prefer === unless you explicitly need coercion.

Self-check

1. What prefix do all variables use?
2. Name three scalar types.

Pitfall: Use === for comparisons—loose == coerces types and causes subtle bugs (0 == 'foo').