How can I run from exception and receive false in this case - laravel

Question

I have this code
function checkIBAN($iban)
{
$iban = strtolower(str_replace(' ','',$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);
try{
$cntr=(in_array(substr($iban,0,2),$Countries)) ? $Countries[substr($iban,0,2)] : false;
if(strlen($iban) == $cntr){
$MovedChar = substr($iban, 4).substr($iban,0,4);
$MovedCharArray = str_split($MovedChar);
$NewString = "";
foreach($MovedCharArray AS $key => $value){
if(!is_numeric($MovedCharArray[$key])){
$MovedCharArray[$key] = $Chars[$MovedCharArray[$key]];
}
$NewString .= $MovedCharArray[$key];
}
if(bcmod($NewString, '97') == 1)
{
return TRUE;
}
else{
return FALSE;
}
}
else{
return FALSE;
}
}catch (Exception $e) {
report($e);
return false;
}
}
And I receive this exception in Laravel
{message: "Undefined offset: 21", exception: "ErrorException",…}
exception
:
"ErrorException"
"Undefined offset: 21" in this string $Countries[substr($iban,0,2)]
How can I run from Exception and receive just a false in this case? Because of that fact that my function which is checking iban must receive only true or false not an Exception. If I receive an Exception that is 500error in Ajax

Answer 1

There are quite a few tested iban validation libraries on the packagist.
https://packagist.org/?q=iban&p=0
I'd use one of these instead.
Much better than some crusty code copied off another stackoverflow question.
A "ErrorException" is laravel's error handler turning a php error into an exception. You can avoid the error by adding checks before doing array access.
Consider this example:
$MovedCharArray[$key] = $Chars[$MovedCharArray[$key]];
It assumes that $MovedCharArray has an index of $key and assumes that $Chars has an index of $MovedCharArray[$key]. If any of those don't exist, you'll get that error.
Add some checks before attempting to access those array elements and you can avoid the error.
if(isset($MovedCharArray[$key]) && isset($Chars[$MovedCharArray[$key]])){
$MovedCharArray[$key] = $Chars[$MovedCharArray[$key]];
}else{
//Some error condition you'll need to deal with.
}