title: How to increment an alphanumeric string in PHP?
body: <p>There's a string, containing characters <code>[a-zA-Z0-9]</code>. This should be 26 * 2 + 10 = 62 possibilities in one character and 62^2 in two. What is the preferred way to increment a value of such a string, so that 'aA', becomes 'aB', etc.? Is there any built-in stuff in PHP, that can help?</p>
  
  <p>I know you can increment a string, but that's only lowercase letters. Essentially, the result should go from 'a' to 'aa' in 61 increments.</p>