Allowing Only Certain Characters In PHP

I need to check to see if a variable contains anything OTHER than a-z A-Z 0-9 and the "." character (full stop). Any help would be appreciated.

From stackoverflow

• if (preg_match("/[^A-Za-z0-9.]/", $myVar)) {
     // make something
  }
  

  The key point here is to use "^" in the [] group - it matches every character except the ones inside brackets.

  Tom Haigh : I think that this would only detect strings consisting of _only_ the unspecified characters - it might be better to use /[^A-Za-z0-9\.]/

  PEZ : Much better. But I still suggest /[^A-Z\d.]/i since it's clearer and less to type. And you don't need to escape the "." inside character classes.

• if (preg_match('/[^A-Z\d.]/i', $var))
    print $var;
  

• There are two ways of doing it.

  Tell whether the variable contains any one character not in the allowed ranges. This is achieved by using a negative character class [^...]:

  preg_match('/[^a-zA-Z0-9\.]/', $your_variable);
  

  Th other alternative is to make sure that every character in the string is in the allowed range:

  !preg_match('/^[a-zA-Z0-9\.]*$/', $your_variable);