Difference between Single and Double quotation marks in PHP

PHP's single quotes and double quotes are not the same as C #, Java, HTML, and Js. PHP single quotes and double quotes are different.

PHP:

Single quotes ('') indicate the output as is. That is to say, the variable name or any other text will be sent to the client without modification.

The variable name in double quotation marks ("") is replaced by the variable value.

For example:

     <?  PHP
  $ Time     =     Date  (  '  Y-m-d h: I: S '  );
  Echo     '  Time: $ time  '  ;  //  Print: Time: $ time  
    Echo     '  <Br/>  '  ;
 Echo     "  Time:  $ Time  "  ;  //  Print: Time: 17:01:20  
  ?> 

We can see that the variables in double quotation marks are replaced before they are declared, while the variable names in single quotation marks are output as they are.