PHP验证信用卡卡号函数

 1 /** 2 ?????* 验证银行卡号是否是信用卡 3 ?????* @param $cardnumber 4 ?????* @return bool 5 ?????*/ 6 ????function validateCard ($cardnumber){ 7 ????????$cardnumber = preg_replace ("/\D|\s/","", $cardnumber); 8 ????????$cardlength = strlen($cardnumber);if($cardlength !=0){ 9 ????????????$parity = $cardlength %2;10 ????????????$sum =0;11 ????????????for($i=0; $i<$cardlength; $i++){12 ????????????????$digit = $cardnumber[$i];13 ????????????????if($i %2== $parity) $digit = $digit *2;14 ????????????????if($digit >9) $digit = $digit -9;15 ????????????????$sum = $sum + $digit;16 ????????????}17 ????????????$valid =($sum %10==0);18 ????????????return $valid;19 ????????}20 ????????return false;21 ????}