check my code and inform me why data is not inserted in database
<!DOCTYPE> <?php session_start(); include("includes/db_connect.php"); ?> <html> <head> <title>Post your add </title> <link rel="stylesheet" href="style.css" media="all"/> </head> <body> <form action="insert_post.php" method="post" enctype="multipart/form-data"> <table width="800" align="center" border="2"> <tr align="center"> <td colspan="6" bgcolor="grey"><h1>Insert New Post: </h1></td> </tr> <tr> <td align="right"><strong>Name:</strong> </td> <td><input type="text" name="name" required/></td> </tr> <tr> <td align="right"><strong>Ad Title:</strong></td> <td><input type="text" name="ad_title" required/></td> </tr> <tr> <td align="right"><strong>Address:</strong></td> <td><input type="text" name="address" required/></td> </tr> <tr> <td align="right"><strong>Country:</strong></td> <td><input type="text" name="country" required/></td> </tr> <tr> <td align="right"><strong>City:</strong></td> <td><input type="text" name="city" required/></td> </tr> <tr> <td align="right"><strong>Category:</strong></td> <td> <select name="cats"> <option value="null">Select a Category</option> <option>Books</option> <?php include("includes/db_connect.php"); if(isset($_GET['edit_cats'])){ $cats_id = $_GET['edit_cats']; $get_cats = "select * from categories where cats_id='$cats_id'"; $run_cats = mysqli_query($con, $get_cats); $row_cats = mysqli_fetch_array($run_cats); $cats_id = $row_cats['cats_id']; $cats_title = $row_cats['cats_title']; } ?> </select> </td> </tr> <tr> <td align="right"><strong>Subcategory:</strong></td> <td> <select name="subcats"> <option value="null">Select a subcategory</option> <option>Books</option> <?php include("includes/db_connect.php"); if(isset($_GET['edit_subcat'])){ $subcats_id = $_GE