The real text is:
Hello\tWorld\r!\"\'\n\u{00a6}\\

Double quotations:

Single quotations:

Single quotations shows the exact value without converting characters - except single questions and backslashes, as I know - but double quotations convert many expressions and characters; as you see. The characters with backlashes that converts to a special string are some thing we call escape characters.

\u{xxxx} (which x is a hexadecimal number) is new in PHP7. You can use it to print out almost every character in UTF-8 Unicode.

Diffrence between ' and "