String interpolation is quick shortcut, allowing to pop up the value of a variable into double quoted String. Remember that any variable with “$” sign into single quote is not a variable, it just treat as a statement.
eg. ‘$num is not a variable’ because num variable is written into single quote.
<?php
$value= 10;
echo "$value is good price of the product"; //<strong>String interpolation</strong>
echo '$value is good price of the product';
?>Code language: HTML, XML (xml)