通过准备好的语句从数据库中获取行 [英] Fetching rows from database via a prepared statement

问题描述

我最初创建了以下查询，以从数据库中返回一些结果.

I initially created the below query to return some results from my database.

$result = mysqli_query($con, "SELECT bookingId, locationName 
                              FROM bookings 
                              WHERE username = '$one'");
$output = array();
while($row = mysqli_fetch_assoc($result)) {
  $output[]=$row;
}
print(json_encode($output));

但是，我现在想使用准备好的语句并尝试了以下方法.但是它总是返回[].这是通过准备好的语句返回行的正确方法.

However, I now want to use prepared statements and have tried the below. But It always returns []. Is this the correct way to return rows via a prepared statement.

$stmt = $con->prepare('SELECT bookingId,locationName
FROM bookings
WHERE username= ?');
$stmt->bind_param('s', $one);
$stmt->execute();
$stmt->bind_result($id, $loc);
$output = array();
while($row = $stmt->fetch()){
$output[] = $row;
}
$stmt->close();

print(json_encode($output));

推荐答案

问题:

与mysqli中的PDO不同，函数fetch()不返回行，它仅返回布尔值或NULL，请检查文档:

Unlike PDO in mysqli the function fetch() does not return a row, it just returns a boolean or NULL, check the docs:

#Value  Description
#TRUE   Success. Data has been fetched
#FALSE  Error occurred
#NULL   No more rows/data exists or data truncation occurred

解决方案

$sql = '
SELECT bookingid, 
       locationname 
FROM   bookings 
WHERE  username = ? 
';
/* prepare statement */
if ($stmt = $con->prepare($sql)) {
    $stmt->bind_param('s', $one);
    $stmt->execute();   
    /* bind variables to prepared statement */
    $stmt->bind_result($id, $loc);
    $json = array();
    /* fetch values */
    if($stmt->fetch()) {
        $json = array('id'=>$id, 'location'=>$loc);
    }else{
        $json = array('error'=>'no record found');
    }
    /* close statement */
    $stmt->close();
}
/* close connection */
$con->close();
print(json_encode($json));

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