Regex with multiple newlines in sequence - php

Question

I'm trying to use PHP's split() (preg_split() is also an option if your answer works with it) to split up a string on 2 or more \r\n's. My current effort is:
split("(\r\n){2,}",$nb);
The problem with this is it matches every time there is 2 or 3 \r\n's, then goes on and finds the next one. This is ineffective with 4 or more \r\n's.
I need all instances of two or more \r\n's to be treated the same as two \r\n's. For example, I'd need
Hello\r\n\r\nMy\r\n\r\n\r\n\r\n\r\n\r\nName is\r\nShadow
to become
array('Hello','My','Name is\r\nShadow');

Answer 1

preg_split() should do it with
$pattern = "/(\\r\\n){2,}/";

Answer 2

What about the following suggestion:
$nb = implode("\r\n", array_filter(explode("\r\n", $nb)));

Answer 3

It works for me:
$nb = "Hello\r\n\r\nMy\r\n\r\n\r\n\r\n\r\n\r\nName is\r\nShadow";
$parts = split("(\r\n){2,}",$nb);
var_dump($parts);
var_dump($parts === array('Hello','My',"Name is\r\nShadow"));
Prints:
array(3) {
[0]=>
string(5) "Hello"
[1]=>
string(2) "My"
[2]=>
string(15) "Name is
Shadow"
}
bool(true)
Note the double quotes in the second test to get the characters represented by \r\n.

Answer 4

Adding the PREG_SPLIT_NO_EMPTY flag to preg_replace() with Tomalak's pattern of "/(\\r\\n){2,}/" accomplished this for me.

Answer 5

\R is shorthand for matching newline sequences across different operating systems. You can prevent empty elements being created at the start and end of your output array by using the PREG_SPLIT_NO_EMPTY flag or you could call trim() on the string before splitting.
Code: (Demo)
$string = "\r\n\r\nHello\r\n\r\nMy\r\n\r\n\r\n\r\n\r\n\r\nName is\r\nShadow\r\n\r\n\r\n\r\n";
var_export(preg_split('~\R{2,}~', $string, 0, PREG_SPLIT_NO_EMPTY));
echo "\n---\n";
var_export(preg_split('~\R{2,}~', trim($string)));
Output from either technique:
array (
0 => 'Hello',
1 => 'My',
2 => 'Name is
Shadow',
)