datatable.php

<?php
// Database details
$db_server   = 'localhost';
$db_username = 'root';
$db_password = '';
$db_name     = 'register';

// Get job (and id)
$job = '';
$id  = '';
if (isset($_GET['job'])){
  $job = $_GET['job'];
  if ($job == 'get_companies' ||
      $job == 'get_company'   ||
      $job == 'add_company'   ||
      $job == 'edit_company'  ||
      $job == 'delete_company'){
    if (isset($_GET['id'])){
      $id = $_GET['id'];
      if (!is_numeric($id)){
        $id = '';
      }
    }
  } else {
    $job = '';
  }
}

// Prepare array
$mysql_data = array();

// Valid job found
if ($job != ''){

  // Connect to database
  $db_connection = mysqli_connect($db_server, $db_username, $db_password, $db_name);
  if (mysqli_connect_errno()){
    $result  = 'error';
    $message = 'Failed to connect to database: ' . mysqli_connect_error();
    $job     = '';
  }

  // Execute job
  if ($job == 'get_companies'){

    // Get companies
    $query = "SELECT * FROM questions ORDER BY id";
    $query = mysqli_query($db_connection, $query);
    if (!$query){
      $result  = 'error';
      $message = 'query error';
    } else {
      $result  = 'success';
      $message = 'query success';

      while ($company = mysqli_fetch_array($query)){
        $functions  = '<div class="function_buttons"><ul>';
        $functions .= '<li class="function_edit"><a data-id="'   . $company['id'] . '" data-name="' . $company['quest_desc'] . '"><span>Edit</span></a></li>';
        $functions .= '<li class="function_delete"><a data-id="' . $company['id'] . '" data-name="' . $company['quest_desc'] . '"><span>Delete</span></a></li>';
        $functions .= '</ul></div>';
        $mysql_data[] = array(
          "quest_desc"   => $company['quest_desc'],
          "ans1"      => $company['ans1'],
          "ans2"      => $company['ans2'],
          "ans3"      => $company['ans3'],
          "ans4"      => $company['ans4'],
          "ans5"      => $company['ans5'],
          "correct_ans" => $company['correct_ans'],
          "functions"    => $functions
        );
      }
    }

  } elseif ($job == 'get_company'){

    // Get company
    if ($id == ''){
      $result  = 'error';
      $message = 'id missing';
    } else {
      $query = "SELECT * FROM questions WHERE id = '" . mysqli_real_escape_string($db_connection, $id) . "'";
      $query = mysqli_query($db_connection, $query);
      if (!$query){
        $result  = 'error';
        $message = 'query error';
      } else {
        $result  = 'success';
        $message = 'query success';
        while ($company = mysqli_fetch_array($query)){
          $mysql_data[] = array(
            "quest_desc"   => $company['quest_desc'],
            "ans1"      => $company['ans1'],
            "ans2"      => $company['ans2'],
            "ans3"      => $company['ans3'],
            "ans4"      => $company['ans4'],
            "ans5"      => $company['ans5'],
            "correct_ans" => $company['correct_ans'],
          );
        }
      }
    }

  } elseif ($job == 'add_company'){

    // Add company
    $query = "INSERT INTO questions SET ";
    if (isset($_GET['quest_desc']))         { $query .= "quest_desc         = '" . mysqli_real_escape_string($db_connection, $_GET['quest_desc'])         . "', "; }

    if (isset($_GET['ans1'])) { $query .= "ans1 = '" . mysqli_real_escape_string($db_connection, $_GET['ans1']) . "', "; }

    if (isset($_GET['ans2']))   { $query .= "ans2   = '" . mysqli_real_escape_string($db_connection, $_GET['ans2'])   . "', "; }

    if (isset($_GET['ans3']))      { $query .= "ans3      = '" . mysqli_real_escape_string($db_connection, $_GET['ans3'])      . "', "; }

    if (isset($_GET['ans4']))  { $query .= "ans4  = '" . mysqli_real_escape_string($db_connection, $_GET['ans4'])  . "', "; }

    if (isset($_GET['ans5']))    { $query .= "ans5    = '" . mysqli_real_escape_string($db_connection, $_GET['ans5'])    . "', "; }

    if (isset($_GET['correct_ans']))   { $query .= "correct_ans   = '" . mysqli_real_escape_string($db_connection, $_GET['correct_ans'])   . "', "; }

    $query = mysqli_query($db_connection, $query);
    if (!$query){
      $result  = 'error';
      $message = 'query error';
    } else {
      $result  = 'success';
      $message = 'query success';
    }

  } elseif ($job == 'edit_company'){

    // Edit company
    if ($id == ''){
      $result  = 'error';
      $message = 'id missing';
    } else {
      $query = "UPDATE it_companies SET ";
      if (isset($_GET['quest_desc']))         { $query .= "quest_desc         = '" . mysqli_real_escape_string($db_connection, $_GET['rank'])         . "', "; }
      if (isset($_GET['ans1'])) { $query .= "ans1 = '" . mysqli_real_escape_string($db_connection, $_GET['ans1']) . "', "; }
      if (isset($_GET['ans2']))   { $query .= "ans2  = '" . mysqli_real_escape_string($db_connection, $_GET['ans2'])   . "', "; }
      if (isset($_GET['ans3']))      { $query .= "ans3      = '" . mysqli_real_escape_string($db_connection, $_GET['ans3'])      . "', "; }
      if (isset($_GET['ans3']))  { $query .= "ans3  = '" . mysqli_real_escape_string($db_connection, $_GET['ans3'])  . "', "; }
      if (isset($_GET['ans4']))    { $query .= "ans4    = '" . mysqli_real_escape_string($db_connection, $_GET['ans4'])    . "', "; }
      if (isset($_GET['ans5']))   { $query .= "ans5   = '" . mysqli_real_escape_string($db_connection, $_GET['ans5'])   . "', "; }
      if (isset($_GET['correct_ans'])) { $query .= "correct_ans = '" . mysqli_real_escape_string($db_connection, $_GET['correct_ans']) . "'";   }
      $query .= "WHERE id = '" . mysqli_real_escape_string($db_connection, $id) . "'";
      $query  = mysqli_query($db_connection, $query);
      if (!$query){
        $result  = 'error';
        $message = 'query error';
      } else {
        $result  = 'success';
        $message = 'query success';
      }
    }

  } elseif ($job == 'delete_company'){

    // Delete company
    if ($id == ''){
      $result  = 'error';
      $message = 'id missing';
    } else {
      $query = "DELETE FROM questions WHERE id = '" . mysqli_real_escape_string($db_connection, $id) . "'";
      $query = mysqli_query($db_connection, $query);
      if (!$query){
        $result  = 'error';
        $message = 'query error';
      } else {
        $result  = 'success';
        $message = 'query success';
      }
    }

  }

  // Close database connection
  mysqli_close($db_connection);

}

// Prepare data
$data = array(
  "result"  => $result,
  "message" => $message,
  "data"    => $mysql_data
);

// Convert PHP array to JSON array
$json_data = json_encode($data);
print $json_data;
?>