In PHP with PDO, how to check if database contains desired value

Question

i am using a form (contains only email) that sends data with ajax to my php file where i need to check if the email that the user entered exists in my database table.

The table contains these columns: id, name, email, timestamp.

In variable $email i have stored the email that the user has added in the form.

i am using PDO to connect to my database with this code

    try {
    $db = new PDO('mysql:unix_socket=/tmp/mysql51.sock;host='. DB_HOST .';dbname='. DB_NAME . ';charset=utf8', DB_USER, DB_PASS);
    } catch (PDOException $e) {
        echo 'Pripojenie zlyhalo: ' . $e->getMessage();
    }

    $query_user = $db->prepare("SELECT COUNT FROM koniecinvite as pocet WHERE email='$email'");
    $query_user->execute();
    $pocet = $query_user->fetchObject();

    if($pocet>0){
        http_response_code(200);
        echo "Email exists";
    }else {
        http_response_code(200);
        echo "Email does not exists";
    }

It is not working. I know i need to get the count of the rows with the email, but i need some help here.

Can somebody help me with this?

EDIT: From error reporting i get "Notice: Object of class stdClass could not be converted to int in "

@CharlotteDunois i get a white blank screen, i think the problem is with ("SELECT COUNT FROM koniecinvite as pocet WHERE email='$email'") — MichalCh, Mar 20 '16 at 13:21
A white page indicates that there is a PHP error. Enable error reporting. — Charlotte Dunois, Mar 20 '16 at 13:22
are you sure you didn't mean to use something like `SELECT COUNT(col)` or `SELECT COUNT(*)`? — Funk Forty Niner, Mar 20 '16 at 13:24
possible duplicate of [check if row exists with mysqli](http://stackoverflow.com/questions/22252904/check-if-row-exists-with-mysqli) — Funk Forty Niner, Mar 20 '16 at 13:25
@CharlotteDunois i get "Notice: Object of class stdClass could not be converted to int in " — MichalCh, Mar 20 '16 at 13:30
Blank screen http://php.net/manual/en/function.error-reporting.php and http://php.net/manual/en/pdo.error-handling.php — Funk Forty Niner, Mar 20 '16 at 13:31

Dimitrios Desyllas · Accepted Answer · 2016-03-20T14:15:27.217

First of all:

SELECT COUNT FROM koniecinvite as pocet WHERE email='$email'"

Should be:

SELECT COUNT(*) FROM koniecinvite as pocet WHERE email='$email'"

Also $email must be escaped because of the danger of SQL Injection: https://en.wikipedia.org/wiki/SQL_injection

So the code snippet that does the query should be (please keep in note that on string I DO NOT USE THE VARIABLE, but instead a :something that will be raplaced by variable with bindParam):

$query_user = $db->prepare("SELECT COUNT FROM koniecinvite as pocet WHERE email=:email");
$query_user->bindParam(":email","$email")
$query_user->execute();

In PHP with PDO, how to check if database contains desired value

1 Answers1