Some quickie dumb credit card decoding stuff

CreditCard.php

<?php

  class CreditCard
  {
    const Industry_ISO = 0;
    const Industry_Airlines = 1;
    const Industry_Airlines2 = 2;
    const Industry_Travel = 3;
    const Industry_Financial = 4;
    const Industry_Financial2 = 5;
    const Industry_Merchandising = 6;
    const Industry_Petroleum = 7;
    const Industry_Telecommunications = 8;
    const Industry_National = 9;

    protected $mNumber = null;
    protected $mChecksum = null;
    protected $mIndustry = null;
    protected $mCountryCode = null; // ISO 3166-1
    protected $mIssuer = null;
    protected $mAccount = null;

    public function __construct( $code )
    {
      $code = filter_var( $code, FILTER_SANITIZE_NUMBER_INT );
      if ( mb_strlen( $code ) < 8
        || mb_strlen( $code ) > 19
        || mb_strpos( $code, '+' ) !== false
        || mb_strpos( $code, '-' ) !== false )
        throw new \RuntimeException( 'Invalid credit card number' );

      $this->mNumber = $code;

      $this->mChecksum = self::checksum( $code );
      if ( $this->mChecksum % 10 != 0 )
        throw new \RuntimeException( 'Invalid credit card checksum' );

      $this->mIndustry = (int)mb_substr( $code, 0, 1 );

      if ( $this->isNational() )
        $this->mCountryCode = mb_substr( $code, 1, 3 );

      $this->mIssuer = mb_substr( $code, 0, 6 );
      $this->mAccount = mb_substr( $code, 6, mb_strlen( $code ) - 7 );
    }

    public function describe()
    {
      printf( "Credit Card\nNumber: %s\nChecksum: %d\nIndustry: %s\nCountry: %s\nIssuer: %s\nAccount Number: %s\n",
        self::grouping( $this->mNumber ),
        $this->mChecksum,
        self::industryName( $this->mIndustry ),
        $this->mCountryCode !== null ? $this->mCountryCode : "None",
        $this->mIssuer,
        $this->mAccount
      );
    }

    public function getChecksum()
    {
      return $this->mChecksum;
    }

    public function getIndustry()
    {
      return $this->mIndustry;
    }

    public function isNational()
    {
      return $this->mIndustry == self::Industry_National;
    }

    public function getCountryCode()
    {
      return $this->mCountryCode;
    }

    public function getIssuer()
    {
      return $this->mIssuer;
    }

    public function getAccount()
    {
      return $this->mAccount;
    }

    public static function industryName( $industry )
    {
      switch ( $industry )
      {
        case self::Industry_ISO: return "ISO/TC68"; break;
        case self::Industry_Airlines: return "Airlines"; break;
        case self::Industry_Airlines2: return "Airlines 2"; break;
        case self::Industry_Travel: return "Travel and Entertainment"; break;
        case self::Industry_Financial: return "Banking and Financial"; break;
        case self::Industry_Financial2: return "Banking and Financial 2"; break;
        case self::Industry_Merchandising: return "Merchandising"; break;
        case self::Industry_Petroleum: return "Petroleum"; break;
        case self::Industry_Telecommunications: return "Telecommunications"; break;
        case self::Industry_National: return "National"; break;
      }
    }

    public static function grouping( $value )
    {
      $out = '';
      $value = str_split( $value );
      for ( $i = 1; $i <= count( $value ); $i++ )
      {
        $out .= $value[$i-1];
        if ( $i % 4 == 0 )
          $out .= ' ';
      }
      return $out;
    }

    public static function checksum( $code )
    {
      $code = str_split( $code );
      $checksum = 0;
      for ( $i = count( $code ) - 1; $i >= 0; $i-- )
      {
        $c = (int)$code[$i];
        if ( ( ( $i - count( $code ) ) % 2 ) == 0 )
          $c *= 2;
        $c = str_split( $c );
        foreach ( $c as $y )
          $checksum += (int)$y;
      }
      return $checksum;
    }
  }

  $cc = new CreditCard( '4485753580439' );
  $cc->describe();
  unset( $cc );