There are 3 formats to include variables in double-quoted strings:

► "part 1 $variable part 2" - This is the simplest format to include a variable in a string. The variable name starts with the dollar sign and ends at the first character that can not be used in variable name. Space is good character to end a variable name.

► "part 1${variable}part 2" - This format helps you to clearly end the variable name. The variable name starts at dollar sign before the open brace (${) and ends at the close brace (}).

► "part 1{$variable}part 2" - This format is also called complex format. You use this format to specify any complex variable expression in the same way as in a normal statement. The variable expression starts at ({$) followed by a variable name and ends at (}).

Here is a PHP script example of different ways to include variables in double-quoted strings:

<?php

$beer = 'Heineken';

echo "$beer's taste is great. ";

echo "He drank some ${beer}s and water. ";

echo "She drank some {$beer}s and water. ";

?>

This script will print:

Heineken's taste is great.

He drank some Heinekens and water.

She drank some Heinekens and water.