8D_How to Calculate The Age Status

<html>
    <head>
    <title>If Statemenet</title
    </head>
<body>
<form method = "get" action = "" >
    Usia <input type = "text" name = "usia" /></br>
    <input type ="submit" name="submit" value="submit" />
    <input type="reset" name="reset" value="reset" /></br>
<?php
echo "Usia : ".$usia = $_GET[usia]." tahun </br>";
if ($usia == " ")
{
    echo "Harap Memasukkan Keterangan Usia";
}
else
{
    if ($usia >=0 && $usia <= 5)
    {
        echo "Status : BALITA";
    }
    else if ($usia >= 6 && $usia <=16)
    {
        echo "Status : Anak-anak";
    }
    else if ($usia >= 17 && $usia <=25)
    {
        echo "Status : REMAJA";
    }
    else if ($usia >= 26 && $usia <=50)
    {
        echo "Status : DEWASA";
    }
    else if ($usia >50)
    {
        echo "Status : TUA";
    }
}
?>
</form>
</body>
</html>