mySQLi准备的语句无法get_result() [英] mySQLi prepared statement unable to get_result()

问题描述

我对mySQLi完全感到困惑.尽管多年来我一直在使用过程性mysql调用，但我希望习惯于为其提供的db security/mySQL注入保护编写准备好的语句.我正在尝试编写一个简单的select语句(是的，我知道为此进行程序调用可提高性能).运行时，我得到所有回声，直到点击$result = $stmt->get_result();组件.在我看来，这一切都相当简单，但是在阅读了数小时的mySQLi手册后，我无所适从.任何想法为什么会失败?

I am totally confused by mySQLi. Although I have been using procedural mysql calls for years, I want to get used to making prepared statements for the db security/mySQL injection protection it offers. I am trying to write a simple select statement (yes I know making a procedural call for this offers performance enhancement). When run, I get all the echoes until I hit the $result = $stmt->get_result(); component. It all seems fairly straightforward to me, but I am at a loss after hours of reading manuals on mySQLi. Any ideas why this would be failing?

*注:这是一个测试环境，虽然没有进行字符的清理/转义，但是我只是将有效内容传递给变量$ username和$ email.而且，我从头到尾都在寻找解决问题的方法.

*note: this is a test environment and while no sanitizing/escaping of characters is taking place, I am only passing valid content into the variables $username and $email. And also, I have looked all over SO to find the solution to my issue.

function checkUsernameEmailAvailability($username, $email) {
    //Instantiate mysqli connection
    @$mysqli = new mysqli(C_HOST,C_USER,C_PASS,C_BASE) or die("Failed to connect to MySQL database...");
    if (!$mysqli)
    {
        echo 'Error: Could not connect to database.  Please try again later...';
        exit;
    } else {
        echo 'mysqli created';
    }

    /* Create a prepared statement */   
    if($stmt = $mysqli -> prepare("SELECT username,email FROM tb_users WHERE username=? OR email=?")) {
        echo '<br />MYSQLi: ';

        /* Bind parameters s - string, b - boolean, i - int, etc */
        $stmt -> bind_param("ss", $username, $email);
        echo '<br />paramsBound...';

        /* Execute it */
        $stmt -> execute();     
        echo '<br />Executed';

        $result = $stmt->get_result();
        echo '<br />Result acquired';

        /* now you can fetch the results into an array - NICE */
        $myrow = $result->fetch_assoc();
        echo '<br />Fetched';


        /* Close statement */
        /$stmt -> close();
        echo '<br />Done mysqli';
    }
}    

此外，每次调用函数时都必须实例化mysqli吗?我假设它们不是像过程mysql中那样持久的数据库连接.是的，我知道这是一个范围问题，并且不，我无法理解此类变量的作用域.当我在函数外部声明它时，进入函数时不可用.

Also, do I have to instantiate a mysqli every time I call a function? I'm assuming they're not persistent db connects like in procedural mysql. Yes, I am aware this is a scope issue, and no I have not been able to understand the scoping of this class variable. When I declared it outside of the function, it was not available when I came into the function.

更新 如果我将第12行更改为:

UPDATE if I change line 12 from:

if($stmt = $mysqli -> prepare("SELECT username,email FROM tb_users WHERE username=? OR email=?")) {

收件人:

    $stmt = $mysqli->stmt_init();
    if($stmt = $mysqli -> prepare("SELECT username,email FROM tb_users WHERE username=? OR email=?")) {
        if(!stmt) echo 'Statement prepared'; else echo 'Statement NOT prepared';

我得到未准备好的声明.现在我更加困惑了...

I get Statement NOT prepared. Now I'm even more confused....

更新: 我联系了我的托管服务提供商，显然支持mySQLi，并且存在mysqlnd驱动程序.也许有一种方法可以简单地对此进行测试?尽管他们通常在过去给了我很多知识渊博的答案.

UPDATE: I contacted my hosting provider and apparently mySQLi is supported, and the mysqlnd driver is present. Perhaps there is a way to simply test this? Although they usually have given me pretty knowledgeable answers in the past.

更新...再次: 我自己检查了服务器功能，发现虽然存在mysqli和PDO，但没有mysqlnd.因此，我了解了为什么get_result()无法工作(我认为需要mysqlnd)，但我仍然不明白为什么预处理语句本身将无法工作.

UPDATE...AGAIN: I checked my server capabilities myself and discovered, while mysqli and PDO are present, mysqlnd is not. Thusly, I understand why get_result() will not work (mysqlnd required I think), I still don't understand why the prepared statement itself will not work.

推荐答案

通过一些检查，即使我的主机上安装了mysqli，显然也不存在mysqlnd驱动程序.因此，不能使用get_result()(PHP手册将get_result定义为mysqlnd依赖)，而是需要进行额外的编码以按我希望的方式处理我的结果.

Through some checking, even though mysqli is installed on my host, apparently the mysqlnd driver is not present. Therefore, get_result() can not be used(php manual defines get_result as mysqlnd dependent), and instead extra coding would need to be done to handle my result the way I would like.

因此，我决定尝试学习PDO的工作原理，几分钟之内，瞧！

Therefore, I decided to try and learn how PDO works, and within minutes, voila!!!

将上面的代码替换为:

function checkUsernameEmailAvailability($username, $email) {

echo 'pdo about to be created';

$dsn = 'mysql:dbname='.C_BASE.';host='.C_HOST;
$user = C_USER;
$password = C_PASS;

try {
    $dbh = new PDO($dsn, $user, $password);
} catch (PDOException $e) {
    echo 'Connection failed: ' . $e->getMessage();
}

$params = array(':username' => $username, ':email' => $email);

try{
$sth = $dbh->prepare('SELECT username,email FROM tb_users WHERE username = :username OR email = :email ');
} catch(PDOException $e) {
    echo 'Prepare failed: ' . $e->getMessage();
}

try{
$sth->execute($params);
} catch(PDOException $e) {
    echo 'Execute failed: ' . $e->getMessage();
}
$result = $sth->fetch(PDO::FETCH_ASSOC);
print_r($result);
}

尽我所能进行错误检查，并且一开始就完全没有问题！

As much error checking as I could think of, and no problems at all first crack at it!

最终密码

Final Code

function checkUsernameEmailAvailability($username, $email) {
    $dsn = 'mysql:dbname='.C_BASE.';host='.C_HOST;
    $user = C_USER;
    $password = C_PASS;
    new PDO($dsn, $user, $password);

    $params = array(':username' => $username, ':email' => $email);

    $sth = $dbh->prepare('SELECT username,email FROM tb_users WHERE username = :username OR email = :email ');
    $sth->execute($params);
    $result = $sth->fetch(PDO::FETCH_ASSOC);

    print_r($result);
}

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