"<<<" 稱為 here doc syntax，PHP 4/5 才有提供這個語法，用來定義「一堆」字串給變數時特別好用，例如：

<?php
$str = <<<EOD
I saw a dog yesterday.
It's very fat.
Too fat to walk.
I tried to help it.
But in vain.
Because it weights 100 KG.
EOD;
?>

$str 字串的值即為：

I saw a dog yesterday.
It's very fat.
Too fat to walk.
I tried to help it.
But in vain.
Because it weights 100 KG.

EOD 為字串的開始與結果，可自定，要注意的是，<<