Here is the fix:

Original Code:

$sum=0;
$mfcStr=”";
if($useKeys==’C')
{
for($i=0;$i<strlen($barnumber);$i+=2)
{
$val=substr($barnumber,$i,2);
if(is_int($val))
$sum+=($i+1)*(int)($val);
elseif($barnumber==chr(129))
$sum+=($i+1)*100;
elseif($barnumber==chr(130))
$sum+=($i+1)*101;
$mfcStr.=$encTable[$val];
}
}

Fixed Code:

$sum=0;
$weight = 0;
$mfcStr=”";
if($useKeys==’C')
{
for($i=0;$i<strlen($barnumber);$i+=2)
{
$weight++;
$val=substr($barnumber,$i,2);
if(is_numeric($val))
$sum+=$weight*(int)($val);
elseif($barnumber==chr(129))
$sum+=$weight*100;
elseif($barnumber==chr(130))
$sum+=$weight*101;
$mfcStr.=$encTable[(int) $val];
}
}

If you read his post he gives some information to why you have to change that stuff.