Frustation with data validation

First, thanks to all who offered suggestions with my "simple ereg question". I have been unable to get anything to work "properly" in spite of many good suggestions. The problem I want to solve is to ensure that input fields have either an integer number or are blank before the program proceeds. I am approaching the problem thusly: for ($i=1;$i<=3;$i++) { echo $_POST["grass_$i"]; // Pollen name echo $_POST["gamt_$i"]; // Pollen amount if (is_int($_POST["gamt_$i"])) { continue; } else

    {
      die("Non-numeric data entered in grass entry field(s).");
    }

} The two echo statements accurately return what data is in the two input fields. The program dies when there is integer data returned in the echo $POST["gamt_$i"] statement. If I negate the expression in the if statement like so : if (!is_int($_POST["gamt_$i"])) the program runs. Isn't that a bit weird? It gets weirder. If I enter an alpha character with if (!is_int($_POST["gamt_$i"])), the program still runs but treats the alpha character as a 0. How should I construct that if statement so that the program will only run with integer data or no data entered into the input fields? TIA Bob Harvey