問(wèn)題描述

$query = $pdo -> prepare("SELECT * FROM Users WHERE Username =:Username");
$query->bindParam(':Username', $name);
$query->execute();

$nameRes = $query->fetch(PDO::FETCH_ASSOC);
if ($nameRes['Username']==$_POST['username']) {
    die ("Username is already in use!");
}   

$query = $pdo -> prepare("SELECT * FROM Users WHERE Email =:Email");
$query->bindParam(':Email', $email);
$query ->execute();
$emailRes = $query->fetch(PDO::FETCH_ASSOC);

if ($emailRes['Email']==$_POST['email']) {
    die ("Email is already in use!");
}

我在我的應(yīng)用程序的注冊(cè)頁(yè)面上有這個(gè)代碼，當(dāng)用戶名可以免費(fèi)使用但電子郵件不是，反之亦然我得到這個(gè)

I have this code on the registration page of my app and when Username is free to use but email is not and vice versa I get this

注意:嘗試訪問(wèn) bool 類型值的數(shù)組偏移量

Notice: Trying to access array offset on value of type bool

好的，結(jié)果返回false，但在這種情況下該怎么辦?注意:這是在 php v7.4 上，同樣的事情在 v7.3 上工作

Ok the result is returning false but what to do in this situation? Note: This is on php v7.4 this same thing was working on v7.3

推薦答案

您收到此錯(cuò)誤可能是因?yàn)樵跀?shù)據(jù)庫(kù)中找不到符合您條件的記錄.

解決此錯(cuò)誤的最簡(jiǎn)單方法是先檢查數(shù)據(jù)庫(kù)是否返回任何內(nèi)容.

The easiest way to solve this error is to check if the database returned anything first.

$emailRes = $query->fetch(PDO::FETCH_ASSOC);
// VVV - Here I am checking if there was anything returned and then I check the condition
if($emailRes && $emailRes['Email']==$_POST['email']) {
    // ...
}

如果您不在乎數(shù)據(jù)庫(kù)是否返回任何內(nèi)容，那么您可以簡(jiǎn)單地提供一個(gè)默認(rèn)值.例如:

If you don't care whether the database returned anything, then you can simply provide a default value. For example:

$emailRes = $query->fetch(PDO::FETCH_ASSOC);
$email = $emailRes['Email'] ?? ''; // default: empty string

使用 PDO 檢查 DB 中是否存在的正確方法是:

The correct way to check for existance in DB using PDO is:

$query = $pdo->prepare("SELECT COUNT(*) FROM Users WHERE Username =:Username");
$query->execute([':Username' => $name]);
if ($query->fetchColumn()) {
    throw new Exception("Username is already in use!");
}

$query = $pdo->prepare("SELECT COUNT(*) FROM Users WHERE Email =:Email");
$query->execute([':Email' => $email]);
if ($query->fetchColumn()) {
    throw new Exception("Email is already in use!");
}

我沒(méi)有在 PHP 中獲取行并再次進(jìn)行比較，而是從數(shù)據(jù)庫(kù)中獲取匹配行的計(jì)數(shù)，并將該計(jì)數(shù)用作 if 語(yǔ)句中的布爾值.fetchColumn() 將從第一行獲取單列，如果我使用 COUNT(*) 我知道總會(huì)有一行.

Instead of fetching the row and doing the comparison again in PHP I am fetching a count of matching rows from the database and I use that count as a boolean in the if statement. fetchColumn() will fetch a single column from the first row and if I use COUNT(*) I know there will always be one row.

您也可以在一個(gè)查詢中完成:

You can also do it in one query:

$query = $pdo->prepare("SELECT COUNT(*) FROM Users WHERE Username =:Username OR  Email =:Email");
$query->execute([':Username' => $name, ':Email' => $email]);
if ($query->fetchColumn()) {
    throw new Exception("Username or email is already in use!");
}

這篇關(guān)于嘗試訪問(wèn) bool 類型值的數(shù)組偏移量的文章就介紹到這了，希望我們推薦的答案對(duì)大家有所幫助，也希望大家多多支持html5模板網(wǎng)！