validate_pno_fi.php

<?php

function validatePNumber($pnumber) {
	// reference: http://en.wikipedia.org/wiki/National_identification_number#Finland
	
	//initial format thingy
	$pnumber = strtoupper($pnumber);
	if(!preg_match('/^([0-9]{6})(\-|\+|A)?([0-9]{3})([0-9A-Y])$/', $pnumber, $matches)) return false;
	
	//loop through each character of $matches[1].$matches[3] and sum them up
	$numstring = $matches[1].$matches[3];
	$summed = 0;
	for ($i = (strlen($numstring)-1), $j = 1; $i >= 0; $i--, $j *= 10)
	{
		$summed += intval($numstring[$i]) * $j;
	}
	
	//validation of checksum and stuff
	$checkmarks = array('0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F','H','J','K','L','M','N','P','R','S','T','U','V','W','X','Y');
	$expected_checkmark = $checkmarks[$summed % 31];
	
	if($expected_checkmark !== $matches[4]) return false;
	
	//apparently the user did not fail, thus passing. logic is undeniable, yo
	return true;

	//some PNOs to test against:
	$testpnos = array(
		'311201A681K', //this one is supposed to fail
		'280289-123J', //this one is supposed to fail
		'870619-249K', //fail because its YYMMDD instead of DDMMYY
		'170193121N',
		'170193-121N',
		'310560-2087',
		'080170-0067',
		'060973-077E',
		'161249-102x',
		'240556-118s',
		'220691-167W',
		'230892-079K',
		'160873-2013',
		'060690A089T',
		'311068-104Y',
		'250769+164V',
		'231057-099T',
		'290688-167M',
		'080275080P',
		'200585-1988',
		'250686-131C',
		'020770-1937',
		'051287-093B',
		'111090-195N',
		'020689-0656',
		'070185-2710',
		'050182-0338',
		'210966-1699',
		'040589-185J',
		'251189-1250',
		'020465-283D',
		'290892-149P',
		'170192-0792',
		'270676-118N',
		'110685-045A',
		'050576-2276',
		'251248-506H',
		'090491-2032',
		'081091-148F',
		'260282-2022',
		'180371-173X',
		'230684-157D',
		'181287-2637',
		'280770-141A',
		'300580-1595',
		'280469-1210',
		'080992-2131',
		'260987-0791',
		'180488-075Y',
		'081276-126H',
		'010883-1168',
		'150184-1267',
		'270487-080N',
		'040786-2117',
		'020292-1106'
	);
}

?>