Wampserver: Using PHP

Question

How to fix this, it displays on localhost;
Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in C. Here where it appears;
if(isset($_POST["getProduct"])){
$limit = 9;
if(isset($_POST["setPage"])){
$pageno = $_POST["pageNumber"];
$start = ($pageno * $limit) - $limit;
}else{
$start = 0;
}
$product_query = "SELECT * FROM products LIMIT $start,$limit";
$run_query = mysqli_query($con,$product_query);
if(mysqli_num_rows($run_query) > 0){
while($row = mysqli_fetch_array($run_query)){
$pro_id = $row['product_id'];
$pro_cat = $row['product_cat'];
$pro_brand = $row['product_brand'];
$pro_title = $row['product_title'];
$pro_price = $row['product_price'];
$pro_image = $row['product_image'];
echo "
<div class='col-md-4'>
<div class='panel panel-info'>
<div class='panel-heading'>$pro_title</div>
<div class='panel-body'>
<img src='product_images/$pro_image' style='width:160px; height:250px;'/>
</div>
<div class='panel-heading'>$.$pro_price.00
<button pid='$pro_id' style='float:right;' id='product' class='btn btn-danger btn-xs'>AddToCart</button>
</div>
</div>
</div>
";
}
}
}

Answer 1

mysqli_num_rows() function expects one of the parameters to be mysqli_result.
Check this: https://w3schools.com/php/func_mysqli_num_rows.asp