PHP function to extract a field value from a database

Question

I'm trying to get a value of a mysql database using a php function. I have a database like this:

NAME     | EMAIL                | PASSWORD  | OTHER
-------------------------------------------------------
example  | example@example.com  | password  | other
-------------------------------------------------------
example2 | example2@example.com | password2 | other2

and in my PHP file I've tried to use this function:

function selectUserField($email, $field, $connection){
    $select_user = "SELECT '$field' FROM users WHERE email='$email' LIMIT 1";
    $result = mysqli_query($connection, $select_user);
    $value = mysqli_fetch_assoc($result);
    return $value[$field];
}

//And I try to echo the result of the function
$connection = new mysqli(DB_HOST, DB_USER, DB_PASSWORD, DB_NAME);

echo selectUserField("example@example.com", "name", $connection);

But as result I get only the field name and not its content (for this example I get " NAME " and not " example "). How can i do to get the content of the database cell?

Answer 1

Try this

function selectUserField($email, $field, $connection){
    $select_user = "SELECT `$field` FROM users WHERE `email`='$email' LIMIT 1"; //wrap it with ` around the field or don't wrap with anything at all
    $result = mysqli_query($connection, $select_user);
    $value = mysqli_fetch_assoc($result);
    return $value[$field];
}

//And I try to echo the result of the function
$connection = new mysqli(DB_HOST, DB_USER, DB_PASSWORD, DB_NAME);

echo selectUserField("example@example.com", "name", $connection);

Answer 2

$ field周围没有引号。

"SELECT $field FROM users WHERE email='$email' LIMIT 1";