PHP replace double-lines with one HTML Break

问题

I am trying to replace all \n\n on my server with the <BR> tag so that a single \n does not turn into <BR>.

Example:

Hello,\n\nThis is an\nexample.\n\nThanks!

goes to:

Hello,<BR>This is an\nexample,<BR>Thanks!

(notice the single \n was not replaced)

When I do the following in PHP, it does not replace the two lines with a break:

$str = str_replace("\n\n", "<br />", $str);

回答1:

Your \n are actually \r\n (which means the input came from a Windows operating system), I suggest you normalize you newlines to the *nix standard first with the following regular expression:

$str = preg_replace('~\r\n?~', "\n", $str);

Then, your original snippet will work (demo):

$str = str_replace("\n\n", '<br />', $str);

---

You could also just do:

$str = str_replace("\r\n\r\n", '<br />', $str);

But that wouldn't work if the input came from Linux or a old Mac OS (which only uses \r).

回答2:

You need to double escape your characters:

Try:

$str = str_replace("\\n\\n", "<br />", $str);

来源：https://stackoverflow.com/questions/10825380/php-replace-double-lines-with-one-html-break