Iterate over each line in a string in PHP

preg_split the variable containing the text, and iterate over the returned array:

foreach(preg_split("/((\r?\n)|(\r\n?))/", $subject) as $line){
    // do stuff with $line
} 

I would like to propose a significantly faster (and memory efficient) alternative: strtok rather than preg_split.

$separator = "\r\n";
$line = strtok($subject, $separator);

while ($line !== false) {
    # do something with $line
    $line = strtok( $separator );
}

Testing the performance, I iterated 100 times over a test file with 17 thousand lines: preg_split took 27.7 seconds, whereas strtok took 1.4 seconds.

Note that though the $separator is defined as "\r\n", strtok will separate on either character - and as of PHP4.1.0, skip empty lines/tokens.

See the strtok manual entry: http://php.net/strtok