当我试图在"storeRating"中调用函数"getAverage"时，我得到一个HTML 500服务器错误。如果我评论掉这个函数，一切都很完美。如何在函数"storeRating"中调用函数getAverage？即使我不注释该函数，代码仍然会检查重复的评级，并将新的评级发布到"评级"表中。请查看getAverage函数中的代码。我需要能够用平均值更新"产品"表中的评级。
以下是我的PHP类
DB功能：
<?php
class DB_TestFunctions {
private $conn;
// constructor
function __construct() {
require_once 'DB_Connect.php';
// connecting to database
$db = new Db_Connect();
$this->conn = $db->connect();
}
// destructor
function __destruct() {
}
// Storing new rating
public function storeRating($pid, $userid, $ratingpnt) {
$stmt = $this->conn->prepare("INSERT INTO rating(ProductID,UserID,prod_rating) VALUES(?, ?, ?)");
$stmt->bind_param("sss", $pid, $userid, $ratingpnt);
$result = $stmt->execute();
$stmt->close();
getAverage($pid);
// check for successful store
/* if ($result) {
$stmt = $this->conn->prepare("SELECT * FROM products WHERE pid = ?");
$stmt->bind_param("s", $pid);
$stmt->execute();
$rating = $stmt->get_result()->fetch_assoc();
$stmt->close();
return $rating;
} else {
return false;
} */
}
/**
* Check if rating exists
*/
public function checkDuplicate($pid, $userid) {
$stmt = $this->conn->prepare("SELECT prod_rating from rating WHERE ProductID = ? AND UserID = ?");
$stmt->bind_param("ss", $pid, $userid);
$stmt->execute();
$stmt->store_result();
if ($stmt->num_rows > 0) {
// user existed
$stmt->close();
return true;
} else {
// user not existed
$stmt->close();
return false;
}
}
public function getAverage($pid){
$stmt = $this->conn->prepare("UPDATE products SET prod_rating = (SELECT AVG(prod_rating) FROM rating WHERE ProductID = ?) WHERE pid = ?");
$stmt->bind_param("s", $pid);
$stmt->execute();
$stmt->close();
}
public function getNewRating($pid){
$stmt = $this->conn->prepare("SELECT * FROM products WHERE pid = ?");
$stmt->bind_param("s", $pid);
$stmt->execute();
$rating = $stmt->get_result()->fetch_assoc();
$stmt->close();
return $rating;
}
}
?>
postRate
<?php
require_once 'include/DB_TestFunctions.php';
$db = new DB_TestFunctions();
// json response array
$response = array("error" => FALSE);
if (isset($_POST['pid']) && isset($_POST['userid']) && isset($_POST['rating'])) {
// receiving the post params
$pid = $_POST['pid'];
$userid = $_POST['userid'];
$rating = $_POST['rating'];
// check if user already rated product
if ($db->checkDuplicate($pid, $userid)) {
// user already rated this product
$response["error"] = TRUE;
$response["error_msg"] = "Rating already exists." ;
echo json_encode($response);
} else {
$db->storeRating($pid, $userid, $rating);
// get new rating
$rating = $db->getNewRating($pid);
if ($rating) {
// Rating successful
$response["error"] = FALSE;
$response["prod_rating"] = $rating["prod_rating"];
echo json_encode($response);
} else {
// Rating failed
$response["error"] = TRUE;
$response["error_msg"] = "Unknown error occurred in posting rating!";
echo json_encode($response);
}
}
} else {
$response["error"] = TRUE;
$response["error_msg"] = "Required parameters (pid, userid or rating) are missing!";
echo json_encode($response);
}
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Test Post Rating</title>
</head>
<body>
<h1>Add Comment</h1>
<form action="postRate.php" method="post">
Product ID:<br />
<input type="text" name="pid" placeholder="Product ID" />
<br /><br />
Userid:<br />
<input type="text" name="userid" placeholder="Username" />
<br /><br />
Rating:<br />
<input type="text" name="rating" placeholder="rating" />
<br /><br />
<input type="submit" value="Rate" />
</form>
</body>
</html>
问题是您正在调用getAverage（），它是yor类的一个方法。因此，您需要$this，这是对当前对象的引用，以便从对象中调用该函数。将您的代码更改为：
$this->getAverage()
会解决你的问题。
您需要调用$this->getAverage()也许您应该看看PHP手册