As designing a new platform we tried to integrate the IBAN numbers. We have to make sure that the IBAN is validated and the IBAN stored to the database is always correct. So what would be a proper way to validate the number?
As the logic was explained in my other question, I've created a function myself. Based on the logic explained in the Wikipedia article find a proper function below. Country specific validation.
Algorithm and character lengths per country at https://en.wikipedia.org/wiki/International_Bank_Account_Number#Validating_the_IBAN.
function checkIBAN($iban)
{
if(strlen($iban) < 5) return false;
$iban = strtolower(str_replace(' ','',$iban));
$Countries = array('al'=>28,'ad'=>24,'at'=>20,'az'=>28,'bh'=>22,'be'=>16,'ba'=>20,'br'=>29,'bg'=>22,'cr'=>21,'hr'=>21,'cy'=>28,'cz'=>24,'dk'=>18,'do'=>28,'ee'=>20,'fo'=>18,'fi'=>18,'fr'=>27,'ge'=>22,'de'=>22,'gi'=>23,'gr'=>27,'gl'=>18,'gt'=>28,'hu'=>28,'is'=>26,'ie'=>22,'il'=>23,'it'=>27,'jo'=>30,'kz'=>20,'kw'=>30,'lv'=>21,'lb'=>28,'li'=>21,'lt'=>20,'lu'=>20,'mk'=>19,'mt'=>31,'mr'=>27,'mu'=>30,'mc'=>27,'md'=>24,'me'=>22,'nl'=>18,'no'=>15,'pk'=>24,'ps'=>29,'pl'=>28,'pt'=>25,'qa'=>29,'ro'=>24,'sm'=>27,'sa'=>24,'rs'=>22,'sk'=>24,'si'=>19,'es'=>24,'se'=>24,'ch'=>21,'tn'=>24,'tr'=>26,'ae'=>23,'gb'=>22,'vg'=>24);
$Chars = array('a'=>10,'b'=>11,'c'=>12,'d'=>13,'e'=>14,'f'=>15,'g'=>16,'h'=>17,'i'=>18,'j'=>19,'k'=>20,'l'=>21,'m'=>22,'n'=>23,'o'=>24,'p'=>25,'q'=>26,'r'=>27,'s'=>28,'t'=>29,'u'=>30,'v'=>31,'w'=>32,'x'=>33,'y'=>34,'z'=>35);
if(array_key_exists(substr($iban,0,2), $Countries) && strlen($iban) == $Countries[substr($iban,0,2)]){
$MovedChar = substr($iban, 4).substr($iban,0,4);
$MovedCharArray = str_split($MovedChar);
$NewString = "";
foreach($MovedCharArray AS $key => $value){
if(!is_numeric($MovedCharArray[$key])){
if(!isset($Chars[$MovedCharArray[$key]])) return false;
$MovedCharArray[$key] = $Chars[$MovedCharArray[$key]];
}
$NewString .= $MovedCharArray[$key];
}
if(bcmod($NewString, '97') == 1)
{
return true;
}
}
return false;
}