String manipulation in php4

[sekxx]

Hello there!
I'm building a website in php/MySQL
in my "resgister" script I want to test the login to check if there is some bad char. in!
Exemple if people put Sek/*@xx as a login ( in regsiter form )
I want to prompt them that there are some bad charactere

How can I get the "ord" of each char. of the $Login
and the length[number of char. of $Login]
Somekind of(not a php script: just an exemple):

PHP Code:

function Good_Char($Login) {
  For(i=0;i=length($login);i++) {
    if ( (ORD($Login)>ord("a"))AND(ORD($Login)<ord("z")) ) {
      return true;
    } else {
      return false;
    }
  }
} 


Thank for your answer.


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