Difference Between Single Quotes and Double Quotes

Whenever we assign any String value to a variable, it must be enclosed in single quotes i.e ( ' ) or double quotes i.e ( " ). But there is a difference in single quotes and double quotes. Below here i am going to explain with the help of codes, please have a look.

Code

<?php
$first_name='Saurabh';
$show1="Hello guys my first name is $first_name.";
$last_name='Sharma';
$show2='Hello guys my last name is $last_name.';
echo $show2;
?>

Output Will be :

Hello guys my last name is $last_name.

But if we wish to print varible $show1 then :-

<?php
$first_name='Saurabh';
$show1="Hello guys my first name is $first_name.";
$last_name='Sharma';
$show2='Hello guys my last name is $last_name.';
echo $show1;
?>

Output Will be :

Hello guys my first name is Saurabh.

Single Quotes : It is used  just for assigning the variable.
Double Quotes : It is basically used for Variable Expansion.

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