表格未显示错误但未插入数据库

I'm trying to make a submission form. It returns errors if fields are empty but doesn't insert the data into table and after submission just reloads the page with header only. I don't know what's wrong as no errors are echoed

My validation

    <?php
    // define variables and initialize with empty values
    $nameErr = $comErr = $catErr =$priceErr =$linkErr ="";
    $name = $description = $category = $price = $link = "";


if ($_SERVER["REQUEST_METHOD"] == "POST") {
print_r($_POST);
        if ($_POST["name"] == "") {
            $nameErr = "Name the app";
        }
        else {
            $name= $_POST["name"];
        }
        if ($_POST["price"] == "") {
            $priceErr = "Price the app";
        }
        else {
            $price= $_POST["price"];
        }
        if ($_POST["link"] == "") {
            $linkErr = "Link the app";
        }
        else {
            $link= $_POST["link"];
        }
            if ($_POST["category"] == "") {
            $catErr = "Missing";
        }
        else {
            $category = $_POST["category"];
        }
        if (empty($_POST["description"])) {
            $comErr = "Missing";
        }
        else {
            $description= $_POST["description"];
        }
     if (empty($rateErr) && empty($comErr) && empty($catErr)&& empty($linkErr) && empty($priceErr)) {
            try {
                $con = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD );
                $con->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
                $sql = "INSERT INTO apps (app_name, category, price, link, description, date_added) VALUES (:name, :category, :price, :link, :description, :date)";

                $stmt = $con->prepare( $sql );
                $stmt->bindValue( ":name", $name);
                $stmt->bindValue( ":category", $category);
                $stmt->bindValue( ":price", $price);
                $stmt->bindValue( ":link", $link);
                $stmt->bindValue( ":description", $description);
                $stmt->bindValue( ":date", now());
                $stmt->execute();
                echo "Submitted successfully";
            }catch( PDOException $e ) {
                echo $e->getMessage();
            }
            }

    }

?>

And the form

    <form method="POST"
 action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">
App name <input type="text" name="name" value="<?php echo htmlspecialchars($name);?>">
<span class="error"><?php echo $nameErr;?></span>
<br />
Price <input type="text" name="price" value="<?php echo htmlspecialchars($price);?>">
<span class="error"><?php echo $priceErr;?></span>
<br />
Download link <input type="text" name="link" value="<?php echo htmlspecialchars($link);?>">
<span class="error"><?php echo $linkErr;?></span>
<br />
<select name="category">
 <option value=""></option>
 <option value="maths">maths</option>
 <option value="driving">driving</option>
 <option value="languages">languages</option>
 <option value="literature">literature</option>
 <option value="science">science</option>
  <option value="psychology">psychology</option>
   <option value="psychology">biology</option>
<option value="IT">IT</option>
 <option value="other">Other</option>
</select>
<span class="error"><?php echo $catErr;?></span>
<br />
<textarea rows="4" cols="50" name="description"  value="<?php echo htmlspecialchars($description);?>">
Enter text here...</textarea>
<span class="error"><?php echo $comErr;?></span>
<input type="submit" name="submit" value="Submit">
</form>

You are not echoing any error. You are returning "Submitted successfully" but you are not inside a function. You should place echo "Submitted successfully" if you want to see this message.

it seems your code is not going through $_SERVER["REQUEST_METHOD"].

Try using if(isset($_POST)) instead and print out $_POST with print_r($_POST), just to verify your form is posting data correctly.

check you database connection code

$con = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD );

replace with the below one,it is working and values get inserted...may be this might also be a problem

$con = new PDO('mysql:host=localhost;dbname=test', $user, $pass);