SQL query for data filtering

Question

I have 6 input fields

<input type="text" class="form-control filter-width namef" placeholder="Product Name">
<input type="text" class="form-control filter-width brandf" placeholder="Brand Name">
<input type="text" class="form-control filter-width catf" placeholder="Category">
<input type="text" class="form-control filter-width sizef" placeholder="Size">
<input type="text" class="form-control filter-width pricef" placeholder="Price">
<input type="text" class="form-control filter-width invf" placeholder="Inventory">

each field is used to filter data. if all fields are filled then it is easy to querying data but I actually don't know using how many fields a user is going to filter. He may filter the data using only name, name and brand name, name and brand name and size, price and inventory. putting conditions using if, elseif and thinking of all possible combinations would be difficult and lengthy task. is there any way to achieve this. Here's my PHP:

$name = $_REQUEST['name'];
        $brand = $_REQUEST['brand'];
        $cat = $_REQUEST['cat'];
        $size = $_REQUEST['size'];
        $price = $_REQUEST['price'];
        $inv = $_REQUEST['inv'];
        if(!empty($name) AND !empty($brand) AND !empty($cat) AND !empty($size) AND !empty($price) AND !empty($inv) ||){
            $sql = "SELECT * FROM products WHERE pname='$name' AND brand_name ='$brand' AND ptype = '$cat' AND psize= '$size' AND sprice = '$price' AND inventory='$inv'";
        }
        else{

        }
        $result = $conn->query($sql);
        if($result->num_rows>0){
            while($row=$result->fetch_assoc()){
                $pid = $row['pid'];
                $pname = $row['pname'];
                $pbrand = $row['brand_name'];
                $pcat = $row['ptype'];
                $pinv = $row['inventory'];
                $pprice = $row['sprice'];
                $psize = $row['psize']; ?>
                <tr id="<?php echo $pid; ?>" class="prod-details"><?php echo "<td>".$pid."</td><td>".$pname."</td><td>".$pbrand."</td>"."<td>".$pcat."</td>"."<td>".$psize."</td>"."<td>".$pprice."</td>"."<td>".$pinv."</td>"; ?></tr> <?php
            }
        } 

Now I don't know what conditions to think and write inside else body

Answer 1

You could aggregate your query string. You may try the following-

$query = "";
    if (!empty($name)) {
            $query += " AND pname='$name'";
    }
    if (!empty($brand)) {
            $query += " AND brand_name ='$brand'";
    }
    if (!empty($cat)) {
            $query += " AND ptype = '$cat'";
    }
    if (!empty($size)) {
            $query += " AND psize= '$size'";
    }
    if (!empty($price)) {
            $query += " AND sprice = '$price'";
    }
    if (!empty($inv)) {
            $query += " AND inventory='$inv'";
    }

    if($query != ""){
         $sql = "SELECT * FROM products WHERE 1=1" . $query;
    }else{
      }

Answer 2

Try following code

<?php

$sql = "SELECT * FROM products WHERE 1=1 AND ";

foreach ($_REQUEST as $key => $value) {
    $columnName = '';
    switch ($key) {
        case 'name':
            $columnName = 'pname';
            break;

        case 'brand':
            $columnName = 'brand_name';
            break;

        case 'cat':
            $columnName = 'ptype';
            break;

        case 'cat':
            $columnName = 'psize';
            break;

        case 'size':
            $columnName = 'ptype';
            break;

        case 'inv':
            $columnName = 'inventory';
            break;
    }

    if (!empty($columnName) && !empty($value)) {
        $sql .= " $columnName='$value' AND";
    }
}

$sql = rtrim($sql, 'AND');

$result = $conn->query($sql);
if($result->num_rows>0){
    while($row=$result->fetch_assoc()){
        $pid = $row['pid'];
        $pname = $row['pname'];
        $pbrand = $row['brand_name'];
        $pcat = $row['ptype'];
        $pinv = $row['inventory'];
        $pprice = $row['sprice'];
        $psize = $row['psize']; ?>
        <tr id="<?php echo $pid; ?>" class="prod-details"><?php echo "<td>".$pid."</td><td>".$pname."</td><td>".$pbrand."</td>"."<td>".$pcat."</td>"."<td>".$psize."</td>"."<td>".$pprice."</td>"."<td>".$pinv."</td>"; ?></tr> <?php
    }
} 

Also please correct me if I am wrong.