The $var (single dollar) is a regular variable with the name var that can hold any value such as a string, integer, float, or other object.
The $$var (double dollar) is a reference variable that contains the $variable’s value.
Lets see an example to understand it clearly:
<?php $x = "xyz"; $$x = 20; echo $x."<br/>"; echo $$x."<br/>"; echo $xyz; ?>
![AND](https://www.tutorialsart.com/wp-content/uploads/2021/05/AND-.png)
Now Lets see an other example to understand it more clearly.
<?php $p="PHP"; $$p="Hypertext Preprocessor"; echo $p. "<br>"; echo $$p. "<br>"; echo "Abbrevation of $p is " . $$p. "</br> </br>"; echo "Abbrevation of $p is " . $PHP; // another way of writting above code ?>
![PHP and](https://www.tutorialsart.com/wp-content/uploads/2021/05/PHP-and-.png)