PHP（mysqli）找到单值

Question

I know how to search using mysqli to find if there is at least one match. How do I go about retrieving another value from a found row. It must just require changing 1 or 2 things.

Imagine I have the following DB:

 ID     |     emailaddress     |    password
 1      |     [e-mail]  |    DUMB1PASS
 2      |     [e-mail] |    DUMB2Pass

I can use the following code to verify if the the email address "[e-mail]" exists. How would I look up the password associated with that row (i.e. the row containing [e-mail]).

$email = "[e-mail]";
$servername = "correct"; $username = "correct"; $DBpass = "correct"; $dbname = "correct";
    $conn = new mysqli($servername, $username, $DBpass, $dbname);
    if ($conn->connect_error)
        {
            die("Connection failed: " . $conn->connect_error);
        } 

    $sql = "SELECT emailaddress FROM registration WHERE emailaddress = '$email'";
    $result = $conn->query($sql);

    if ($result->num_rows > 0)
        {
            echo "we found a match";
        } 
    else
        {
            echo "we did not find a match";
        }

I imagine I can do something like:

$email = "[e-mail]";
$servername = "correct"; $username = "correct"; $DBpass = "correct"; $dbname = "correct";
    $conn = new mysqli($servername, $username, $DBpass, $dbname);
    if ($conn->connect_error)
        {
            die("Connection failed: " . $conn->connect_error);
        } 

    $sql = "SELECT password FROM registration WHERE emailaddress = '$email'";
    $result = $conn->query($sql);

    if ($result->num_rows > 0)
        {
            echo "the value is '$result'";
        } 
    else
        {
            echo "we did not find a match";
        }

However, it produces this error:

Catchable fatal error: Object of class mysqli_result could not be converted to string in MYPAGE on line XX.

I think that the cause of this is likely that $result is an array or something. However, I don't know enough about sql/php to know if that is the problem, or how to pull the result from it if it is the case.

I'd really appreciate any help.

Answer 1

You need to fetch the row first, try this:

if ($result->num_rows) {
  $row = $result->fetch_row();
  echo 'the value is: ', $row[0];
}