致命错误：未捕获的错误：在 [重复] 上调用成员函数 close()

Question

错误：

致命错误：未捕获的错误：调用成员函数 close() on C:\xampp\htdocs\Project\script\register.php:69 中的布尔值

堆栈跟踪：#0 C:\xampp\htdocs\Project\index.php(2): include_once() #1 {main} 在 C:\xampp\htdocs\Project\script\register.php 中抛出在线69

当我传递通过验证的正确数据时发生错误。

文件：

<?php 
include_once 'functions.php';
include_once 'dbconnect.php';
// Returns the request method used to access the page
if ($_SERVER["REQUEST_METHOD"] == "POST"){
    $err="";


// Validation .... 
 .....
// End of it

 $prep_stmt = "SELECT id FROM members WHERE email = ? LIMIT 1";
$stmt = $sql_db->prepare($prep_stmt);

// check existing email  
if ($stmt) {
    $stmt->bind_param('s', $email);
    $stmt->execute();
    $stmt->store_result();

    if ($stmt->num_rows == 1) {
        // A user with this email address already exists
        $err .= '<p class="error">A user with this email address already exists.</p>';
                    $stmt->close();
    }
} else {
    $err .= '<p class="error">Database error Line 39</p>';
            $stmt->close();
}

// check existing username
$prep_stmt = "SELECT id FROM members WHERE username = ? LIMIT 1";
$stmt = $sql_db->prepare($prep_stmt);

if ($stmt) {
    $stmt->bind_param('s', $username);
    $stmt->execute();
    $stmt->store_result();

            if ($stmt->num_rows == 1) {
                    // A user with this username already exists
                    $err .= '<p class="error">A user with this username already exists</p>';
                    $stmt->close();
            }
    } else {
            $err .= '<p class="error">Database error line 55</p>';
            $stmt->close();
    }

// Hashing, salting and inserting the values.
   ....
// End of file.

搜索了一些答案，为什么会出现问题，但什么也没找到。

Another thread like this - $stmt->close() 在 if 函数中。

Answer 1

if ($stmt) {
    $stmt->bind_param('s', $email);
    $stmt->execute();
    $stmt->store_result();

    if ($stmt->num_rows == 1) {
        // A user with this email address already exists
        $err .= '<p class="error">A user with this email address already exists.</p>';
                    $stmt->close();
    }
} else {
    $err .= '<p class="error">Database error Line 39</p>';
    // Remove this. $stmt does not exist here due to your if/else condition
    //$stmt->close();  
}