So evidently:
\n = CR (Carriage Return) // Used as a new line character in Unix
\r = LF (Line Feed) // Used as a new line character in Mac OS
\r\n = CR + LF // Used as a new line character in Windows
(char)13 = \n = CR // Same as \n
but then I also heard that for HTML textarea, when it's submitted and parsed by a php script, all new lines are converted to \r\n regardless of the platform
is this true and can I rely on this or am I completely mistaken?
ie. if I wanna do explode() based on a new line, can I use '\r\n' as the delimiter regardless of whether or not the user is using mac, pc, etc
All newlines should be converted in \r\n by the spec.
So you could indeed do a simple explode("\r\n", $theContent) no matter the platform used.
P.S.
\r is only used on old(er) Macs. Nowadays Macs also use the *nix style line breaks (\n).
You could try preg_split, which will use a regular expression to split up the string. Within this regular expression you can match on all 3 new line variants.
$ArrayOfResults = preg_split( '/\r\n|\r|\n/', $YourStringToExplode );
It depends on what you want to achieve. If you are doing this eventually to display / format it as HTML, you can as well use the nl2br() function or possibly use str_replace like this:
$val = str_replace( array("\n","\r","\r\n"), '<br />', $val );
In case you want to just get an array of all lines, I would suggest you use all 3 characters ("\n","\r","\r\n") for explode