PHP在objective-c中返回不同的值

Question

In php this line

      for($i = 0; $i < strlen($string); $i++){
        $keychar = substr($key, ($i % strlen($key))-1,1);
        echo $keychar;
    }
returns `70684292517 `

And if i make the equivalent of this in objective-c it returns a whole different value.

 for (int i = 0; i < string.length; i++) {
        NSString *_keychar = [key substringWithRange:NSMakeRange((i % key.length)-1,1)];
//The fix
NSString *_keychar = [key substringWithRange:NSMakeRange(((i % key.length) ? (i % key.length) : (key.length) )-1,1)];
        NSLog(@"%@",_keychar);
    }

    returns `068429251`

So, why isn't the obj-c code returning the same value as the php one(how it should be)? What am i doing wrong? string has a length of 11 and the key has a value of 0684292517

FIXED