[Resolved] ereg code needed

[ThaSpY]

hey, i dont think it really takes too long to write up a 1 line ereg, but if any of you can spare 2 minutes, i need one that checks to see that the variable ONLY contains a-z, A-Z, 0-9, underscore, and plus sign's (+). Nothing else! if you could write this up for me i would be grateful. (ive tried lots and lots, and i cant seem to master how ereg works so thats why i have to ask, sorry!)

[mrhappiness]

if (preg_match('%[^a-z0-9_+]%i', $subject))
  ech 'invalid';