Why I can't Pass values to the database using php-CodePudding

I have built an ISBN generator using PHP. However, Once ISBN Number is generated it's not stored in the database.

Here is the index.php

<form id="isbn-form" action="generate-isbn.php" method="POST">
  <label for="title">Book Title:</label><br>
  <input type="text" id="title" name="title"><br>
  <label for="author">Author:</label><br>
  <input type="text" id="author" name="author"><br>
  <button type="submit">Generate ISBN</button>
</form>

<script>
  const form = document.getElementById("isbn-form");
  form.addEventListener("submit", async (event) => {
    event.preventDefault();

    // Get the form data
    const formData = new FormData(form);

    // Send a POST request to the server
    const response = await fetch("generate-isbn.php", {
      method: "POST",
      body: formData,
    });

    // Get the generated ISBN number
    const data = await response.json();
    const isbn = data.isbn;

    // Display the ISBN number
    alert(`Your ISBN number is: ${isbn}`);
  });
</script>

Here is the isbn.php

function generate_unique_isbn() {
    // Generate a unique ISBN
    do {
      // Generate the first three digits (ISBN agency)
      $isbn = rand(100, 999) . "-";
  
      // Generate the language code
      $isbn .= rand(0, 9) . "-";
  
      // Generate the book identifier using a cryptographically secure random number generator
      $isbn .= bin2hex(random_bytes(4)) . "-";
  
      // Calculate the check digit
      $check_digit = 0;
      for ($i = 0; $i < strlen($isbn); $i  ) {
        if ($i % 2 == 0) {
          $check_digit  = (int)$isbn[$i];
        } else {
          $check_digit  = 3 * (int)$isbn[$i];
        }
      }
      $check_digit = 10 - ($check_digit % 10);
      if ($check_digit == 10) {
        $check_digit = 0;
      }
      $isbn .= $check_digit;
  
      // Connect to the database
      $conn = new mysqli("localhost", "root", "", "isbn");
  
      // Check if the ISBN is already in the database
      $result = $conn->query("SELECT * FROM books WHERE isbn = '$isbn'");
  
      // Close the database connection
      $conn->close();
    } while ($result->num_rows > 0);
  
    return $isbn;
  }

Here is the generate-isbn.php

<?php

require "isbn.php";

header("Content-Type: application/json");

// Get the form data
$title = $_POST["title"];
$author = $_POST["author"];

// Generate a unique ISBN number
$isbn = generate_unique_isbn();

// Save the book to the database
$conn = new mysqli("localhost", "root", "", "isbn");
$conn->query("INSERT INTO books (isbn, title, author) VALUES ('$isbn', '$title', '$author')");
$conn->close();

echo json_encode(["isbn" => $isbn]);
?>

Why the values are not passing? Save the book to the database code in the generate-isbn.php. Values are generated but only one value is stored in the database. If I want to save the generated value in the database I have to delete the previous value that was stored in the database and run the script. Then it gets stored, After it doesn't store then I have to re-run the process delete the value an run the code. What could be the issue?

CodePudding user response：

The id column in your books table is primary key but you also have to set it AUTO_ICREMENT. Then you can insert rows more than one.