Question

I tried this:

$result = mysql_query("SELECT * from business WHERE ptype = '".$_GET["ptype"]."' AND state = '".$_GET["state"]."' AND city = '".$_GET["city"]."'") or die(mysql_error());   

but if I don’t put 3 GET’s I get an error from MySql:

localhost/get_allinfo.php?ptype=PUB&state=Center

Then I get a MySQL error

I tried this:
but it doesn’t matter if I put “state” in URL $_GET["ptype"]) & (isset($_GET["state"]))

I get the result from “ptype” only

    if (isset($_GET["ptype"])) {
    $ptype = $_GET["ptype"];
    $result = mysql_query("SELECT * from business WHERE ptype = '$ptype'") or die(mysql_error());

}elseif(isset($_GET["ptype"]) & (isset($_GET["state"]))){
    $ptype = $_GET["ptype"];
    $state = $_GET["state"];
    $result = mysql_query("SELECT * from business WHERE ptype = '$ptype' and WHERE state = '$state") or die(mysql_error());
}else {

    $result = mysql_query("SELECT * FROM `business`") or die(mysql_error());
}

Answer 1

This should make it a bit more robust:

$sql = 'SELECT * from business';
$arrQueryString = array();
if(isset($_GET['ptype'])) $arrQueryString[] = 'ptype="'.$_GET['ptype'].'"';
if(isset($_GET['state'])) $arrQueryString[] = 'state="'.$_GET['state'].'"';
if(isset($_GET['city'])) $arrQueryString[] = 'city="'.$_GET['city'].'"';
$sql .= (count($arrQueryString)) ? ' WHERE '.implode(' AND ',$arrQueryString) : '';
$result = mysql_query($sql) or die(mysql_error());