PHP: get relative path expression

The following code calculate the difference of paths given and return a relative path expression.

 


function getCommonPos($s0,$s1)
{
  $len=strlen($s0);
  $len1=strlen($s1);
  if($len1<$len)
    {
      $len=$len1;
    }
  while($s0[$i]==$s1[$i] && ++$i<$len1);
  return $i;
}

function diffStr($s0, $s1)
{
  $pos=getCommonPos($s0,$s1);
  $end=strrpos(substr($s0,0,$pos),"\\");
  return substr($s0,$end);
}

function countSlashes($str)
{
  return substr_count($str,"\\");
}

function getRelativePath($p0,$p1)
{
  $p0=realpath($p0);
  $p1=realpath($p1);
  $dir=diffStr($p0,$p1);

  if(!empty($dir))
    {
      $n=countSlashes($dir);
      $path="";
      for($i=0;$i<$n;$i++)
    {
      $path.="..";
      if($i<$n-1)
        {
          $path.="\\";
        }
    }
    }
  $newDir=diffStr($p0,$p1);
  $newDir=$path.$newDir;
  
  if(empty($newDir))
    $newDir=".";

  return $newDir;
}