How can variables be properly included in a string in PHP?

To properly include variables in a string in PHP, you can use double quotes ("") instead of single quotes (''). This allows you to directly embed variables within the string by placing them inside curly braces {}. This is known as variable interpolation. Example:

$name = "John";
$age = 30;

// Using double quotes for variable interpolation
$string = "Hello, my name is {$name} and I am {$age} years old.";
echo $string;