function luhn_check($number)
{

	 /* Luhn algorithm number checker - (c) 2005-2008 - planzero.org            *
	 * This code has been released into the public domain, however please      *
	 * give credit to the original author where possible.                      */
	 
	  // Strip any non-digits (useful for credit card numbers with spaces and hyphens)
	  $number=preg_replace('/\D/', '', $number);
	 
	  // Set the string length and parity
	  $number_length=strlen($number);
	  $parity=$number_length % 2;
	 
	  // Loop through each digit and do the maths
	  $total=0;
	  for ($i=0; $i<$number_length; $i++) {
		$digit=$number[$i];
		// Multiply alternate digits by two
		if ($i % 2 == $parity) {
		  $digit*=2;
		  // If the sum is two digits, add them together (in effect)
		  if ($digit > 9) {
			$digit-=9;
		  }
		}
		// Total up the digits
		$total+=$digit;
	  }
	 
	  // If the total mod 10 equals 0, the number is valid
	  return ($total % 10 == 0) ? TRUE : FALSE;
 }

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