When do I use PHP_EOL instead of \n and vice-versa ? Ajax/Jquery client problem

Question

I have a php parser that split a given string by line-breaks, doing something like this:

$lines = explode(PHP_EOL,$content);

The parser works fine when working on server side. However, when I pass the content via post by ajax (using jquery's $.post method) the problem arises: line breaks are not recogniezed. So after almost an hour of tests and head-aches I decided to changed PHP_EOL by "\n" and it worked:

$lines = explode("\n",$content);

Now it works! Damn it I lost so much time! Could somebody explain me when use PHP_EOL and "\n" properly, so I can save time in the future? Appreciate your kind answers ;)

Answer 1

The constant PHP_EOL should generally be used for platform-specific output.

• Mostly for file output really.
• Actually the file functions already transform \n ←→ \r\n on Windows systems unless used in fopen(…, "wb") binary mode.

For file input you should prefer \n however. While most network protocols (HTTP) are supposed to use \r\n, that's not guaranteed.

• Therefore it's best to break up on \n and remove any optional \r manually:

  $lines = array_map("rtrim", explode("\n", $content));
  

  Or use the file(…, FILE_IGNORE_NEW_LINES) function right away, to leave EOL handling to PHP or auto_detect_line_endings.

• A more robust and terser alternative is using preg_split() and a regexp:

  $lines = preg_split("/\R/", $content);
  

  The \R placeholder detects any combination of \r + \n. So would be safest, and even work for Classic MacOS ≤ 9 text files (rarely seen in practice).

  ^{Obligatory microoptimization note:
  While regex has a cost, it's surprisingly often speedier than manual loops and string postprocessing in PHP.}

And there are a few classic examples where you should avoid PHP_EOL due to its platform-ambiguity:

• Manual generation of network protocol payloads, such as HTTP over fsockopen().
• For mail() and MIME construction (which really, you shouldn't do tediously yourself anyway).
• File output, if you want to consistently write just Unix \n newlines regardless of environment.

So use a literal "\r\n" combination when not writing to files, but preparing data for a specific context that expects network linebreaks.