Validate IBAN

<
function _isValidIBAN($data, $reformat = true, $countryCode=null, $printErrors=false){
 
 
	$str = $data['account_number'];
 
	if(!empty($str)){
		if($reformat){
			$str = preg_replace('/[\W_]+/', '', strtoupper($str) );	
 
		}
		$errors = array();
		if( 4 > strlen($str) ||  strlen($str) > 34 ){
			$errors[] = 'Invalid string length';
		}
 
		if(is_numeric($str[0])  || is_numeric($str[1])){
			$errors[] = 'Invalid chars at 0, 1';
		}
		if(!is_numeric($str[2]) || !is_numeric($str[3])){
			$errors[] = 'Invalid chars at 3, 4';
		}
 
		if(!empty($countryCode)){
 
			if(!in_array(strtolower(substr($str, 0, 2)), array_map('strtolower', $countryCode))  ){
				$errors[] = 'Invalid Country code. Only accepting '. implode(', ', $countryCode);
			}
		}
 
		$ibanReplaceChars = range('A','Z');
 
		foreach (range(10,35) as $tempvalue) {
			$ibanReplaceValues[]=strval($tempvalue);
		}
 
 
		$tmpIBAN = substr($str, 4).substr($str, 0, 4);
 
		$tmpIBAN = str_replace($ibanReplaceChars, $ibanReplaceValues, $tmpIBAN);
 
		$tmpValue = intval(substr($tmpIBAN, 0, 1));
 
		for ($i = 1; $i < strlen($tmpIBAN); $i++) {
		    $tmpValue *= 10;
		    $tmpValue += intval(substr($tmpIBAN,$i,1));
		    $tmpValue %= 97;
		}
 
		if ($tmpValue != 1) {
		    $errors[] = 'Invalid checksum';
		}
 
		if($printErrors){
			echo implode("\n", $errors);
		}
 
		if(empty($errors)){
			return true;
		}
	}
 
	return false;
}