title: How to check if string contains only specified character set?
body: <p>I'm working on string and I wonder which way is best to check if string contains only specified character set:</p>
  
  <pre><code>@  ∆  SP  0  ¡  P  ¿  p 
  £  _  !  1  A  Q  a  q 
  $  Φ  "  2  B  R  b  r 
  ¥  Γ  #  3  C  S  c  s 
  è  Λ  ¤  4  D  T  d  t 
  é  O  %  5  E  U  e  u 
  ù  Π  &amp;  6  F  V  f  v 
  ì  Ψ  '  7  G  W  g  w 
  ò  Σ  (  8  H  X  h  x 
  Ç  Θ  )  9  I  Y  i  y 
  LF  Ξ  *  :  J  Z  j  z 
  Ø  1)  +  ;  K  Ä  k  ä 
  ø  Æ  ,  &lt;  L  Ö  l  ö 
  CR  æ  q  =  M  Ñ  m  ñ 
  Å  ß  .  &gt;  N  Ü  n  ü 
  å  É  /  ?  O  §  o  à 
  </code></pre>
  
  <p>I was trying to make it done by eregi and regexp, but didn't success.
  Other way is to convert each char to decimal and check if it is smaller than &lt; 137, or check each element by in_array() - which I find weak.</p>
  
  <p>Anyone have better solution?</p>
  
  <p>Thanks in advance.</p>