如何将 MySQL 代码转换为 PDO 语句？

Question

我需要将第一个 if 语句更改为 PDO 语句，但我不确定如何 go 关于它。 请问有人可以帮忙吗？

当用户提交表单时，我希望他们的 email 地址从数据库的用户表中提取到网站的此页面中，使用他们在注册时分配的编号 $id。

$table = 'suggestions';
$id = (isset($_SESSION['u_id']) ? $_SESSION['u_id'] : null);

if ( NULL !== $id) {

  $sql = mysqli_query($conn, "SELECT email FROM users WHERE u_id='$id'");
  $fetch = mysqli_fetch_assoc($sql);
  $email = $fetch['email'];

}

$email;
$optionOne = '';
$optionTwo = '';
$suggestions = selectAll($table);


if (isset($_POST['new-suggestion'])) {
  global $conn;

  $id;
  $email;
  $optionOne = $_POST['optionOne'];
  $optionTwo = $_POST['optionTwo'];
  $sql = "INSERT INTO $table (user_id, email, option_1, option_2) VALUES (?, ?, ?, ?)";

  if (!empty($optionOne) && !empty($optionTwo)) {
    $stmt = $conn->prepare($sql);
    $stmt->bind_param('ssss', $id, $email, $optionOne, $optionTwo);
    $stmt->execute();

  } else {
    echo "All options must be entered";
  }
}

Answer 1

建立联系

首先，您需要将mysqli连接替换为PDO一个（或至少在mysqli旁边添加PDO连接）。

// Define database connection parameters
$db_host = "127.0.0.1";
$db_name = "name_of_database";
$db_user = "user_name";
$db_pass = "user_password";


// Create a connection to the MySQL database using PDO
$pdo = new pdo(
    "mysql:host={$db_host};dbname={$db_name}",
    $db_user,
    $db_pass,
    [
        PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
        PDO::ATTR_EMULATE_PREPARES => FALSE
    ]
);

更新您的代码

使用mysqli和PDO准备的语句

将变量数据放入 SQL 查询时，使用准备好的语句几乎总是更好。 它不仅更安全（如果数据来自任何类型的用户生成的输入），而且更易于阅读，并且更容易使用不同的值多次运行。

使用mysqli准备查询：

$sql   = "SELECT column1, column2 FROM table WHERE column3 = ? AND column4 = ?";
$query = $mysqli->prepare($sql);
$query->bind_param("si", $string_condition, $int_condition);
$query->execute();
$query->store_result();
$query->bind_result($column1, $column2);
$query->fetch();

echo "Column1: {$column1}<br>";
echo "Column2: {$column2}";

使用PDO准备查询：

$sql   = "SELECT column1, column2 FROM table WHERE column3 = ? AND column4 = ?";
$query = $pdo->prepare($sql);
$query->execute([$string_condition, $int_condition]);
$row   = $query->fetchObject();
# $row = $query->fetch(); // Alternative to get indexed and/or associative array

echo "Column1: {$row->column1}<br>";
echo "Column2: {$row->column2}";

更新代码

// Using the NULL coalescing operator here is shorter than a ternary
$id = $_SESSION['u_id'] ?? NULL;

if($id) {
    $sql   = "SELECT email FROM users WHERE u_id = ?";
    $query = $pdo->prepare($sql);    // Prepare the query
    $query->execute([$id]);          // Bind the parameter and execute the query
    $email = $query->fetchColumn();  // Return the value from the database
}

// Putting "$email" on a line by itself does nothing for your code. The only
// thing it does is generate a "Notice" if it hasn't been defined earlier in
// the code. Best use:
//    - The ternary operator: $email = (isset($email)) ? $email : "";
//    - The NULL coalescing operator: $email = $email ?? "";
//    - OR initialize it earlier in code, before the first `if`, like: $email = "";
// N.B. Instead of "" you could use NULL or FALSE as well. Basically in this case 
//    anything that equates to BOOL(FALSE); so we can use them in `if` statements
//    so the following (2 commented lines and 1 uncommented) are effectively
//    interchangeable.
$email = $email ?? "";
# $email = $email ?? FALSE; 
# $email = $email ?? NULL;

// Presumably you will also want to change this function to PDO and prepared statements?
// Although it doesn't actually do anything in the code provided?
$suggestions = selectAll($table);  

// Same as with email, we're just going to use the NULL coalescing operator.
// Note: in this case you had used the third option from above - I've just
//   changed it so there is less bloat.
$optionOne     = $_POST['optionOne'] ?? "";
$optionTwo     = $_POST['optionTwo'] ?? "";
$newSuggestion = $_POST['new-suggestion'] ?? "";

// There's no point nesting `if` statements like this when there doesn't appear to be any
// additional code executed based on the out come of each statement? Just put it into one.
// We now don't need to use empty etc. because an empty, false, or null string all.
// equate to FALSE.
if($newSuggestion && $id && $email && $optionOne && $optionTwo) {
    // Not sure why you've made the the table name a variable UNLESS you have multiple tables
    // with exactly the same columns etc. and need to place in different ones at different
    // times. Which seems unlikely so I've just put the table name inline.
    $sql   = "INSERT INTO suggestions (user_id, email, option_1, option_2) VALUES (?, ?, ?, ?)";
    $query = $pdo->prepare($sql);
    $query->execute([$id, $email, $optionOne, $optionTwo]);
}
else{
    echo "All options must be entered";
}

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$id = $_SESSION['u_id'] ?? NULL;

if($id) {
    $sql   = "SELECT email FROM users WHERE u_id = ?";
    $query = $pdo->prepare($sql);
    $query->execute([$id]);
    $email = $query->fetchColumn();
}
$email       = $email ?? "";
$suggestions = selectAll($table);  

$optionOne     = $_POST['optionOne'] ?? "";
$optionTwo     = $_POST['optionTwo'] ?? "";
$newSuggestion = $_POST['new-suggestion'] ?? "";

if($newSuggestion && $id && $email && $optionOne && $optionTwo) {
    $sql   = "INSERT INTO suggestions (user_id, email, option_1, option_2) VALUES (?, ?, ?, ?)";
    $query = $pdo->prepare($sql);
    $query->execute([$id, $email, $optionOne, $optionTwo]);
}
else{
    echo "All options must be entered";
}