问题
I'm new to PHP and don't understand what the point of <<<_END is. Could someone please explain when this should be used? I've looked at various examples and they all seem to have HTML embedded within them. But I can use HTML without the <<<_END tags, so why should I use them? I tried searching the manual, but I keep finding the end() method for arrays.
回答1:
It's the start of a heredoc. you can do:
$data = <<< _END
You can write anything you want in between the start and end
_END;
_END can be just about anything. You could put EOF or STUFF. as long as you use the same thing at the start and the finish.
回答2:
This signifies the beginning of a heredoc (a multi-line string that allows you to use quotation marks in the middle, unescaped) that ends when you encounter the _END
It can be useful to define HTML in one of these if the goal is to assign it to a variable or pass it to a function rather than printing it to the web server immediately.
回答3:
That syntax is called heredoc
<<<_END
some text
_END
Basically, it's a way of writing a string without worrying about escaping quotes and so on.
As you've mentioned, it doesn't really provide a lot of benefit over other string formats - although, it does mean you can write a block of HTML without escaping out of PHP with ?>
It also isn't too popular as its use generally goes against the practice of seperating content from logic by embedding the content in the middle of your script.
回答4:
Does this help? http://www.php.net/manual/en/language.types.string.php#language.types.string.syntax.heredoc
It allows you to echo out a block of text (just the same as with echo "words";), but without using the beginning/ending quotes, and without having to escape contained double quotes. Read the manual link above for more detail.
回答5:
It's a heredoc. It's just a way of defining a string.
来源：https://stackoverflow.com/questions/4675814/what-is-end