Inserting Variables into Strings in PHP

In PHP, single and double quotes for strings are not entirely equivalent. The fact is that variables can be inserted into double-quoted strings - and the value of these variables will be substituted in their place.

Let's try it in practice. Suppose we have some variable:

php<?php
  $str = 'aaa';
?>

First, let's insert this variable into some string using the concatenation operation:

php<?php
  $str = 'aaa';
  echo 'xxx ' . $str . ' yyy';
?>

Now let's change the quotes of our string to double quotes and insert the variable into it:

php<?php
  $str = 'aaa';
  echo "xxx $str yyy";
?>

php<?php
  $name = 'user';
  echo 'hello, ' . $name . '!';
?>