title: php upper and lowercase without built in function
body: <p>Hey guys i want to convert a string from lowercase to uppercase and vice versa without using any built in functions strtoupper or strtolower in php, can anyone help me please.</p>
  
  <p>edit: I can use some other functions to do the job, like substr(), ord(), chr(), strlen(), str_replace.</p>
  
  <p>This was my first question here so could not specify what i needed in best way. 
  I was given task to do the job in these mentioned functions without use of arrays either.</p>
  
  <p>...next time i will be careful.</p>