The ' <<< ' in PHP

This is the PHP delimiter (heredoc syntax: Http://php.net/manual/zh/language.types.string.php#language.types.string.syntax.heredoc)

In
<<<eof and EOF; Text that can be used without escaping, such as single and double quotes

Typically used to output long HTML text or text assignments

Example:

$str = <<<eof
123123123
EOF;

The EOF here is a marker that begins with EOF and must end with EOF
You can change it to another character.
It must also be noted that EOF must have a semicolon at the end, and that EOF must be shelf, without any characters, including spaces.

The ' <<< ' in PHP