Get line number from preg_match_all()

Question

I\'m using PHP\'s preg_match_all() to search a string imported using file_get_contents(). The regex returns matches but I would like to know at which line number those matches a

Answer 1

Using preg_match_all with the PREG_OFFSET_CAPTURE flag is necessary to solve this problem, the code comments should explain what kind of array preg_match_all returns and how the line numbers can be calculated:

// Given string to do a match with
$string = "\n\nabc\nwhatever\n\ndef";

// Match "abc" and "def" in a string
if(preg_match_all("#(abc).*(def)#si", $string, $matches, PREG_OFFSET_CAPTURE)) {
  // Now $matches[0][0][0] contains the complete matching string
  // $matches[1][0][0] contains the results for the first substring (abc)
  // $matches[2][0][0] contains the results for the second substring (def)
  // $matches[0][0][1] contains the string position of the complete matching string
  // $matches[1][0][1] contains the string position of the first substring (abc)
  // $matches[2][0][1] contains the string position of the second substring (def)

  // First (abc) match line number
  // Cut off the original string at the matching position, then count
  // number of line breaks (\n) for that subset of a string
  $line = substr_count(substr($string, 0, $matches[1][0][1]), "\n") + 1;
  echo $line . "\n";

  // Second (def) match line number
  // Cut off the original string at the matching position, then count
  // number of line breaks (\n) for that subset of a string
  $line = substr_count(substr($string, 0, $matches[2][0][1]), "\n") + 1;
  echo $line . "\n";
}

This will return 3 for the first substring and 6 for the second substring. You can change \n to \r\n or \r if you use different newlines.