Variables start with a dollar sign. PHP's built-in types are:

<?php
$name    = "Alice";          // string
$age     = 30;               // integer
$price   = 9.99;             // float
$active  = true;             // bool
$nothing = null;             // null
$colours = ["red","green"];  // array

// Check a type at runtime
var_dump($price);   // float(9.99)
gettype($age);      // "integer"
is_string($name);   // true

String concatenation uses the dot operator:

<?php
$greeting = "Hello, " . $name . "! You are " . $age . " years old.";
// Or use double-quoted strings with variable interpolation:
$greeting = "Hello, $name! You are {$age} years old.";

PHP will silently coerce types in arithmetic. Use strict comparison (===) to avoid surprises:

<?php
var_dump("2" + 3);         // int(5)  - string coerced to int
var_dump("2" == 2);        // bool(true)  - loose comparison
var_dump("2" === 2);       // bool(false) - strict comparison (different types)