What's this kind of syntax in PHP?

Question

$test= <<

I have never see it before. What\'s it used for?

Answer 1

This is called HEREDOC syntax, which is a way to define strings, on multiple lines, with variable interpolation.

Quoting the manual page:

Heredoc text behaves just like a double-quoted string, without the double quotes. This means that quotes in a heredoc do not need to be escaped, but the escape codes listed above can still be used. Variables are expanded, but the same care must be taken when expressing complex variables inside a heredoc as with strings.

(There is more to read, that I didn't copy-paste from the manual page)

And, as a very quick and simple example:

$a = 'World';
$string = <<
  Hello, $a!

MARKER;
echo $string;

It will give you this output:

Hello, World!

And this HTML source:

  Hello, World!