Fetching rows from database via a prepared statement

问题

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));

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));

回答1:

Problem:

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

Solution

$sql = '
SELECT bookingid, 
       locationname 
FROM   bookings 
WHERE  username = ? 
';
/* prepare statement */
if ($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));

回答2:

You could try the following (instead of using bind_result()):

$result = $stmt->get_result();

$output = array();
while ($row = $result->fetch_assoc()) {
    $output[] = $row['bookingId'];
}

It basically makes your row already an array. Could be that this works better for you. If you're not doing anything else in the while loop, you can do what RobP suggested, and just use fetch_all:

mysqli_fetch_all($result, MYSQLI_ASSOC);

来源：https://stackoverflow.com/questions/27585423/fetching-rows-from-database-via-a-prepared-statement

标签

php

json

mysqli

prepared-statement