CI VIN Number Form Validation Callback

vin_number_callback.php

	//--------------------------------------------------------------------

	/**
	 * VIN Number Form Callback to verify that the VIN number is correct.
	 *
	 * Original VIN Check Code came from below link, no sense reinventing wheels
	 * @link {http://stackoverflow.com/questions/3831764/php-vin-number-validation-code}
	 *
	 * @param string $vin VIN Number value sent from Form Validation Library.
	 *
	 * @return bool
	 */
	public function _vin_check($vin)
	{

	   if ( ! preg_match('/^[^\Wioq]{17}$/', $vin)) 
	   { 
	   		$this->form_validation->set_message('_vin_check', 'The %s is not the correct length.');
	        return FALSE; 
	    }

	    $weights = array(8, 7, 6, 5, 4, 3, 2, 10, 0, 9, 8, 7, 6, 5, 4, 3, 2);

	    $transliterations = array(
	        "a" => 1, "b" => 2, "c" => 3, "d" => 4,
	        "e" => 5, "f" => 6, "g" => 7, "h" => 8,
	        "j" => 1, "k" => 2, "l" => 3, "m" => 4,
	        "n" => 5, "p" => 7, "r" => 9, "s" => 2,
	        "t" => 3, "u" => 4, "v" => 5, "w" => 6,
	        "x" => 7, "y" => 8, "z" => 9
	    );

	    $sum = 0;

	    for ($i = 0; $i < strlen($vin); $i++) 
	    { // loop through characters of VIN
	        // add transliterations * weight of their positions to get the sum
	        if ( ! is_numeric($vin{$i})) 
	        {
	            $sum += $transliterations[$vin{$i}] * $weights[$i];
	        } 
	        else 
	        {
	            $sum += $vin{$i} * $weights[$i];
	        }
	    }

	    // find checkdigit by taking the mod of the sum

	    $checkdigit = $sum % 11;

	    if ($checkdigit == 10) 
	    { // checkdigit of 10 is represented by "X"
	        $checkdigit = "x";
	    }

	    $valid = (bool) ($checkdigit == $vin{8});

		// Need to Add Check for Correct VIN Number Here.
		if ($valid == FALSE)
		{
			$this->form_validation->set_message('_vin_check', 'The %s is not valid.');
			return FALSE;
		}
		else
		{
			return TRUE;
		}
	}//end _vin_check() - Callback function


	//--------------------------------------------------------------------	

There are problems with this code I believe 00000000000354888 would be considered valid . You should not use length of in the for loop as it could be changed while code is in motion .. always lowercase ?