php信用卡卡号算法函数实例分享

<?php
/**
* 信用卡卡号检测函数
* edit by www.jb200.com
*/
function validateCard ( $cardnumber )
{
     $cardnumber = preg_replace ( " /D|s/ " , "" , $cardnumber ) ;  # strip any non-digits
     $cardlength = strlen ( $cardnumber ) ;
     if ( $cardlength != 0 )
     {
         $parity = $cardlength % 2 ;
         $sum = 0 ;
         for ( $i = 0 ; $i < $cardlength ; $i ++ )
         {
             $digit = $cardnumber [ $i ] ;
             if ( $i % 2 == $parity ) $digit = $digit * 2 ;
                 if ( $digit > 9 ) $digit = $digit - 9 ;
                     $sum = $sum + $digit ;
         }
         $valid = ( $sum % 10 == 0 ) ;
         return $valid ;
     }
     return false ;
}
?>