Delete record from SQLite database using form button

Created a form that successfully inserts a record from a form into a SQLite database. Trying to also add a delete button but i am unsure on how to execute the query properly. Here is my code:

index.php

<input id="submit" type="submit" name="input" value="Input">
<input id="submit" type="submit" name="delete" value="Delete">

post.php

if (!empty($_POST['input'])) {
  header("location:index.php");
  $stmt = $conn->prepare("INSERT INTO stock (name, gender, age) VALUES   (:name, :gender, :age)");
  $stmt->execute(array(':name' => $_POST['name'],
                                       ':gender' => $_POST['gender'],
                                       ':age' => $_POST['age']));
}

elseif (!empty($_POST['delete'])) {
  header("location:index.php");
  $stmt = $conn->prepare("DELETE FROM stock WHERE name = ':name' AND gender = ':gender' AND age = 'age'");

}