A string in PHP is a series of single-byte characters (i.e. there is no native Unicode support) that can be specified in four ways:
Displays things almost completely "as is". Variables and most escape sequences will not be interpreted. The exception is that to display a literal single quote, one can escape it with a back slash ', and to display a back slash, one can escape it with another backslash \
Unlike a single-quoted string, simple variable names and escape sequences in the strings will be evaluated. Curly braces (as in the last example) can be used to isolate complex variable names.
There are limits: Array"
But we can get around them by wrapping the whole variable in braces: Success
In a heredoc string, variable names and escape sequences are parsed in a similar manner to double- uoted strings, though braces are not available for complex variable names. The start of the string is delimited by <<
A nowdoc string is like the single-quoted version of heredoc, although not even the most basic escape sequences are evaluated. The identifier at the beginning of the string is wrapped in single quotes.
nothing is parsed (not even escaped apostrophes \' and backslashes \\.)"