How to find the second-to-last occurrence of a character within a string?

Question

If possible, using only standard PHP functions like substr(), strrpos(), strpos(), etc.

Answer 1

Search for a regexp (plz correct me if I'm wrong, and how to write it in PHP):

    r'x[^x]*x[^x]*$'.replace('x',your_char)

Answer 2

General solution for any number of backwards steps:

function strrpos_count($haystack, $needle, $count)
{
    if($count <= 0)
        return false;

    $len = strlen($haystack);
    $pos = $len;

    for($i = 0; $i < $count && $pos; $i++)
        $pos = strrpos($haystack, $needle, $pos - $len - 1);

    return $pos;
}

Answer 3

First, find the last position:

$last = strrpos($haystack, $needle);
if ($last === false) {
  return false;
}

From there, find the 2nd last:

$next_to_last = strrpos($haystack, $needle, $last - strlen($haystack) - 1);

Answer 4

I don't think this can be done with strrpos because the position start does not work in the way you would expect.

There is afaik not any obvious way, but this function should do it. (Not really tested, but I think it work).

    /** Return the position of the second last needle in haystack or false if nothing is found. I really hate functions with return types that depend on their input, but this function is made to look like the similary php functions (strpos, strrpos and so on) */

// Needle must be a char. If you want it to be a string instead, just substr
// length of needle instead of 1 in this example.
    function findSecondLastChar($needle,$haystack) {
      $found=0;
      for($pos=strlen($haystack)-1;$pos>=0;$pos--) {
        if(substr($haystack,$pos,1)==$needle) {
          if($found++ == 1)
            return $pos;
        }
      }
       // If we reach this, nothing were found
       return false;
    }

Answer 5

With strpos:

$pos = -1; $last = null; $secondLast = null;
while (($pos = strpos($haystack, $needle, $pos+1)) !== false) {
    $secondLast = $last;
    $last = $pos;
}
if (!is_null($secondLast)) {
    echo 'second last occured on '.$secondLast;
}