PHP function to verify whether the credit card number is correct

This article mainly shares with you the PHP function to verify whether the credit card number is correct. I hope it can help everyone.

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 ;
    }

The above is the detailed content of PHP function to verify whether the credit card number is correct. For more information, please follow other related articles on the PHP Chinese website!