A string is a group of characters, where a character is equivalent to a byte. This implies PHP just supports a 256-character set and subsequently doesn’t offer local Unicode support.
Single quote (‘) :-
Single quote strings are the most straightforward approach to indicate string. Single quote is utilized to indicate string when we need the string to be actually as it is composed.
Here, used single quote string so not displayed or output your data value. Here work as a string. If you want to print correct data value then add in Double quote string.
Double quote (“):-
Double quoted strings are used to print any value of a variable in PHP. It will show a large group of got away characters, and variables in the strings will be assessed. A significant point here is that you can use curly braces to isolate the name of the variable you want to be evaluated.
Here, Double quote string uses to print or display variables of data.
Heredoc (<<<):- It works similarly as the double quote.
Here, used heredoc syntax in this where (echo <<< ANYDATA) then, right if (echo <<< ANYDATA ) you want to any space or any tab then show error.
Nowdoc (<<<‘ ‘):- It works similarly as a single quote.