How to store a single column of a single row out of a MySQLi prepared statement in a PHP variable?

问题

I'm very new to PHP and MySQL and I'm looking for a solution to store a single value of a database row in a variable using a prepared statement.

Right now this is the prepared statement and execution:

$emailsql = $conn->prepare("SELECT email FROM User WHERE email = ? limit 1;");
$emailsql->bind_param('s', $email);
$emailsql->execute();

I tried get_result(), fetch(), fetch_object() and I'm out of ideas and google search results.

回答1:

You need to add to your code the binding of the result to a specific variable

$emailsql->bind_result($emailResult);

And you fetch it :

while($emailsql->fetch()){   
  printf ($emailResult); 
}

So this should be it:

$emailsql = $conn->prepare("SELECT email FROM User WHERE email = ? limit 1;");
$emailsql->bind_param('s', $email);
$emailsql->execute();
$emailsql->bind_result($emailResult); 
while($emailsql->fetch()){   
  printf ($emailResult); 
}

In case you need the variable outside the loop I would take this approach:

$theEmail;
$emailsql = $conn->prepare("SELECT email FROM User WHERE email = ? limit 1;");
$emailsql->bind_param('s', $email);
$emailsql->execute();
$emailsql->bind_result($emailResult); 
while($emailsql->fetch()){   
  $theEmail=$emailResult; 
}

Note that you would need an array in order to query more than one email.

Another cleaner approach as @YourCommonSense suggested would be avoiding the loop like so:

$theEmail;
$emailsql = $conn->prepare("SELECT email FROM User WHERE email = ? limit 1;");
$emailsql->bind_param('s', $email);
$emailsql->execute();
$emailsql->bind_result($emailResult); 
$emailsql->fetch();   
printf($emailResult);

回答2:

There are two ways. Either that bind-result way explained in the other answer, or a conventional method of fetching a regular array

$stmt = $conn->prepare("SELECT 1 FROM User WHERE email = ?;");
$stmt->bind_param('s', $email);
$stmt->execute();
$res = $stmt->get_result(); 
$row = $res->fetch_row();
$value = $row ? $row[0] : null;

Given all that, you may consider the how bad mysqli's usability is, compared to PDO:

$stmt = $conn->prepare("SELECT 1 FROM User WHERE email = ? limit 1;");
$stmt->execute([$email]);
$value = $stmt->fetchColumn();

来源：https://stackoverflow.com/questions/37116740/how-to-store-a-single-column-of-a-single-row-out-of-a-mysqli-prepared-statement

标签

php

mysqli