prepared语句的准备与select查询失败

Question

$stmt2 = $con->prepare("SELECT * FROM forum_posts WHERE `category_id`=? AND `topic_id`=?");

if ( !$stmt2 || $con->error ) {

    die('Select forum posts prepare() failed: ' . htmlspecialchars($con->error));

}

if(!$stmt2->bind_param('ii', $cid, $tid)) {

    die('Select forum posts bind_param() failed: ' . htmlspecialchars($stmt2->error));

}

if(!$stmt2->execute()) {

    die('Select forum posts execute() failed: ' . htmlspecialchars($stmt2->error));

}

使用Chris Brand的答案-它把我带到绑定参数并停在那里...

<?php
$con = mysqli_connect("localhost", "root", "", "db");
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}
$cid = $_GET['cid'];
$tid = $_GET['tid'];
$userid = ( isset( $_SESSION['user'] ) ? $_SESSION['user'] : "" );

//Prepared SELECT stmt to get forum topics
$stmt = $con->prepare("SELECT * FROM forum_topics WHERE `category_id`=? AND id=? LIMIT 1");
if (!$stmt || $con->error ) {
    die('Select topics prepare() failed: ' . htmlspecialchars($con->error));
}
if(!$stmt->bind_param('ii', $cid, $tid)) {
    die('Select topics bind_param() failed: ' . htmlspecialchars($stmt->error));
}
if(!$stmt->execute()) {
    die('Select topics execute() failed: ' . htmlspecialchars($stmt->error));
}
$stmt->store_result();
$numrows = $stmt->num_rows;
if($numrows == 1){
    echo "<table width='100%'>";
    if ( $_SESSION['user'] ) { 
        echo "<tr><td colspan='2'><input type='submit' value='Add Reply' onClick=\"window.location = 
    'forum_post_reply.php?cid=".$cid."$tid=".$tid."'\"> <hr />";
    } else {
        echo "<tr><td colspan='2'><p>Please log in to add your reply</p><hr /></td></tr>";
    }

    foreach($stmt as $row) {

        //Prepared SELECT stmt to get forum posts
        if($stmt2 = $con->prepare("SELECT * FROM forum_posts WHERE `category_id`=? AND `topic_id`=?")) {
        //var_dump($stmt2);
        if (!$stmt2) {
            die('Select forum posts prepare() failed: ' . htmlspecialchars($con->error));
        }
        } else {
        var_dump($con->error);
        }
        if(!$stmt2->bind_param('ii', $cid, $tid)) {
            die('Select forum posts bind_param() failed: ' . htmlspecialchars($stmt2->error));
        }
        if(!$stmt2->execute()) {
            die('Select forum posts execute() failed: ' . htmlspecialchars($stmt2->error));
        }
        //while($row2 = mysqli_fetch_assoc($stmt2)){
        foreach($stmt2 as $row2) {  
            echo "<tr><td valign='top' style='border: 1px solid #000000;'>
            <div style='min-height: 125px;'>".$row['topic_title']."<br />
            by ".$row2['post_creator']." - " .$row2['post_date']. "<hr />" . $row2['post_content'] ."</div></td>
            <td width='200' valign='top' align='center' style='border: 1px solid #000000;'>User Info Here!</td></tr>
            <tr><td colspan='2'><hr /></td></tr>";
        }
    }
} else {
    echo "<p>This topic does not exist.</p>";
}

用阿卜杜拉的回答：

$con = mysqli_connect("localhost", "root", "", "db");
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}
$cid = $_GET['cid'];
$tid = $_GET['tid'];
$userid = ( isset( $_SESSION['user'] ) ? $_SESSION['user'] : "" );

//Prepared SELECT stmt to get forum topics
$stmt = $con->prepare("SELECT * FROM forum_topics WHERE `category_id`=? AND id=? LIMIT 1");
if (!$stmt || $con->error ) {
    die('Select topics prepare() failed: ' . htmlspecialchars($con->error));
}
if(!$stmt->bind_param('ii', $cid, $tid)) {
    die('Select topics bind_param() failed: ' . htmlspecialchars($stmt->error));
}
if(!$stmt->execute()) {
    die('Select topics execute() failed: ' . htmlspecialchars($stmt->error));
}
$stmt->store_result();
$numrows = $stmt->num_rows;
if($numrows == 1){
    echo "<table width='100%'>";
    if ( $_SESSION['user'] ) { 
        echo "<tr><td colspan='2'><input type='submit' value='Add Reply' onClick=\"window.location = 
    'forum_post_reply.php?cid=".$cid."$tid=".$tid."'\"> <hr />";
    } else {
        echo "<tr><td colspan='2'><p>Please log in to add your reply</p><hr /></td></tr>";
    }

    foreach($stmt as $row) {

            //Prepared SELECT stmt to get forum posts
        $stmt2 = $mysqli::prepare("SELECT * FROM forum_posts WHERE category_id='value' AND topic_id='value'");
        //var_dump($stmt2);
        //if ( !$stmt2 || $con->error ) {
            //die('Select forum posts prepare() failed: ' . htmlspecialchars($con->error));
    //  }
        //var_dump($con->error);
        if(!mysqli_stmt_bind_param($stmt2,"i", $cid, $tid)) //i means intiger
        {
            die('Select forum posts bind_param() failed: ' . htmlspecialchars($stmt2->error));
        }
        if(!mysqli_stmt_execute($stmt2)) {
            die('Select forum posts execute() failed: ' . htmlspecialchars($stmt2->error));
        }
        //while($row2 = mysqli_fetch_assoc($stmt2)){
        foreach($stmt2 as $row2) {  
            echo "<tr><td valign='top' style='border: 1px solid #000000;'>
            <div style='min-height: 125px;'>".$row['topic_title']."<br />
            by ".$row2['post_creator']." - " .$row2['post_date']. "<hr />" . $row2['post_content'] ."</div></td>
            <td width='200' valign='top' align='center' style='border: 1px solid #000000;'>User Info Here!</td></tr>
            <tr><td colspan='2'><hr /></td></tr>";
        }
    }
} else {
    echo "<p>This topic does not exist.</p>";
}

Answer 1

Prepared Statements失败的原因如下：

1）数据库未连接。

2）查询未正确生成

/* First check the correction */
    if ( mysqli_connect_errno() ) {
        printf("Connect failed: %s\n", mysqli_connect_error());
    }

/* Secondly try to print out the query after this statement*/

$stmt2 = $con->prepare("SELECT * FROM forum_posts WHERE `category_id`=? AND `topic_id`=?");
var_dump($stmt2);