#1 You have an error in the EAN13 Check digit

[Lachezar Todorov]

The function should look like this:

function EAN13CheckDigit($str){
$sum=0;
$code=str_split($str);
$sum=($code[1]+$code[3]+$code[5]+$code[7]+$code[9]+$code[11])*3;
$sum+=$code[0]+$code[2]+$code[4]+$code[6]+$code[8]+$code[10];

$sum = ($sum % 10 == 0) ? 0 : (10-($sum %10));

return $sum;
}

The problem was the case when sums MOD is 0 .. then the check digit is 10 but it should be 0.