Filter system not working

Question

Hello so i made my filter system its a simple one only location and price range are set for now everything looks like this : so the problem i have is that min and max price range filter doesn't work location filter are working as it should be the only problem i face is min and max price got no error or warning nothing but eater nothing happens to.

php code above :

$cat1 = '';

if(isset($_GET["catid"])){

    $p1 = '';
    $p2 = '';
    $catid = $_GET["catid"];
    $l1 = substr($catid,0,1);
    $l2 = substr($catid,1,1);
    $p1 = "CAT".$l1;
    if(!empty($l2)){
        $p2 = "CAT".$l1."-".$l2;
        $p3 = $p2;
    }
    $cat1 = @$lang[$p1];
    $cat2 = @$lang[$p2];   
}

$postid = '';
$userid = '';
$pricemin = '';
$pricemax = '';
$location = '';

if(isset($_POST["filter"])){

$pricemin = $_POST["min"];
$pricemax = $_POST["max"];
$location = $_POST["location"];
}

main page code :

 <div class="fp">
        <div class="filter">
            <b style="padding-left: 10px;">Filters:</b>
            <form class="filterform" action="" method="post"><br>
                Location: <br>
                <input name="location" ><br>
                Price Range:<br>
                Min:<input type="text" name="min" size="5"> Max:<input type="text" name="max" size="5"><br><br>
                <input class="submit-button" type="submit" name="filter" value="Filter">
            </form>
        </div>
        <div class="posts">
            <div id="adcat"><?php
                if(!empty($cat2)){
                    ?>
                    <a href="cat.php?catid=<?php echo $l1; ?>" ><?php echo $cat1." » "; ?></a><span><?php echo $cat2; ?></span>
                    <?php
                } else {
                echo "<font color='grey'>".$cat1."</font>";
                }
                        ?>
            </div><br><br>
            <div id="detailformscat">
                    <?php
                    if(empty($p1) && empty($p2)){
                        $sql = "SELECT * FROM posts p JOIN images i ON p.id = i.postid ";
                        if(!empty($location)){
                            $sql .= "AND location='$location'";
                        }
                        if(!empty($min)){
                            $sql.= "AND price>='$min' ";
                        }
                        if(!empty($max)){
                            $sql.= "AND price<='$max' ";
                        }
                    } else if(!empty($p2)){
                        $sql = "SELECT * FROM posts p JOIN images i ON p.id = i.postid WHERE catid='$p2' ";
                        if(!empty($location)){
                            $sql .= "AND location='$location'";
                        }
                        if(!empty($min)){
                            $sql.= "AND price>='$min' ";
                        }
                        if(!empty($max)){
                            $sql.= "AND price<='$max' ";
                        }
                    } else {
                        $sql = "SELECT * FROM posts p JOIN images i ON p.id = i.postid WHERE p.catid LIKE '$p1%' ";
                        if(!empty($location)){
                            $sql .= "AND location='$location'";
                        }
                        if(!empty($min)){
                            $sql.= "AND price>='$min' ";
                        }
                        if(!empty($max)){
                            $sql.= "AND price<='$max' ";
                        }
                    }
                    $res = mysqli_query($connect,$sql);
                     while ($row = mysqli_fetch_assoc($res)) {
                         $postid = $row["postid"];
                         ?>
                        <div id="ads">
                            <div id="adfavcat">
                                    <?php if(!isset($_SESSION["userid"])) { ?>
                                    <a href="post.php?login=false" ><img src="image/+fav.png" width="40px" height="40px"></a>
                                    <?php } else { 

                                            $userid = $_SESSION["userid"];
                                            $sql2 = "SELECT * FROM fav WHERE userid='$userid' AND postid='$postid' ";
                                            $res2 = mysqli_query($connect,$sql2);
                                            $rowcount = mysqli_num_rows($res2);

                                            if ($rowcount > 0){ ?>
                                                <a href="cat.php?catid=<?php echo $catid; ?>&delete&id=<?php echo $postid?>" ><img src="image/xfav.png" width="40px" height="40px"></a>
                                            <?php
                                            } else { ?>
                                            <a href="cat.php?catid=<?php echo $catid; ?>&add&id=<?php echo $postid; ?>" ><img src="image/+fav.png" width="40px" height="40px"></a>
                                            <?php }
                                    } ?>

                            </div>
                            <div id="titlepic">
                            <a href="review.php?id=<?php echo $postid; ?>"><?php echo $row["title"]; ?></a><br>
                            <a href="review.php?id=<?php echo $postid; ?>"><img src="<?php if(!empty($row["path1"])) { echo $row["path1"]; } else echo "image/noimage.png"; ?>" height="100px" width="150px"></a>
                            </div>
                            <div id="datescat">
                                <b>Date Added:</b> <?php echo date('m/d/Y H:i', $row["dateadded"]); ?><br>
                                <b>Renew Date:</b> <?php if($row["renewdate"] > 0){ echo date('m/d/Y H:i', $row["renewdate"]); } ?><br>
                                <b>Location:</b> <?php echo $row["location"]; ?><br>
                                <b>Price:</b> <?php echo $row["price"]."&pound"; ?><br>

                            </div>
                        </div>
                        <hr width="100%">
                        <?php
                     }

                ?>
        </div>
          </div>
    </div>

Answer 1

I think it's because you are treating the price as a string, in the sql query you wrote

$sql.= "AND price>='$min' ";

Try with cast/sanitize/filter input variables $min & $max to integers and removing the quotes.

--- by the way, I personally would also change some things:

1. use atom instead of brackets
2. use an ORM and remove the query from the html page (the view)
3. if 2 is not possible, try to move all php logic to the php file instead of the html part
4. remove all that IFs and try to write a code without lots of repetitions

---

You are also joining the tables instead of filtering, try changing

$sql = "SELECT * FROM posts p JOIN images i ON p.id = i.postid ";

with

$sql = "SELECT * FROM posts p JOIN images i ON p.id = i.postid WHERE p.id > 0 ";

---

change

$pricemin = '';
$pricemax = '';

with

$min = '';
$max = '';