Character boundary statement

Question

Character boundary statement
1). Write three less than signs (<<<) after the equal sign after the variable.
2). Then write characters after <<< (English uppercase characters are recommended). As in the following example: ABC
3). Then change the line and write any characters you want
4). After writing, go to the top line. At the beginning of the line, write the characters following <<< and a semicolon. As in the following example: ABC;

<?php

$dingjie = <<<ABC
If
you have to be in front of this kid

Noodles & lt; br/& gt;
plus a paragraph
& lt; i & gt; How far</h1>
ABC;
?>

Answer 1

I still don't know what this is for.