Кавычки в PHP

[netcat-na-diary]

$name = 'Dolly';
echo 'Hello, $name'; // Hello, $name

If you replace the single quotes in the second line with double ones (see quotes_02.php), $nameis processed and
its value is displayed onscreen:

$name = 'Dolly';
echo "Hello, $name"; // Hello, Dolly