FWIW, a while back I came across an interesting variation on typing the alphabet for use in translate(): type the keyboard layout instead, thus:

translate($string, 'QWERTYUIOPASDFGHJKLZXCVBNM', 'qwertyuiopasdfghjklzxcvbnm')

It's much easier to type (for a non-touch-typist like me, anyway) and that, to my mind, makes it less susceptible to the kind of slip you made in your code.

translate($string,
          'MR JOCK, TV QUIZ PHD, BAGS FEW LYNX',
          'mr jock, tv quiz phd, bags few lynx')

Cheers,
Wendell