title: Set string to a specified length in PHP
body: <p>I need to have a string that has a specified length and replace the excess characters with a letter. </p>
  
  <p>e.g.</p>
  
  <p>My original string is : "JOHNDOESMITH". The length should be up to 25 characters only.
  I need my string to become "XXXXXXXXXXXXXJOHNDOESMITH" (13 X's and 12 chars from the original string). </p>
  
  <p>Anybody please tell me how to achieve this? Is there a string function for this? I've been racking my brains out for quite some time now and I still can't find a solution. </p>