How to check If user exists in MySQL database?

Question

How to check if a user exists in the database already?

I have variable $name = $user_profile['name']; It successfully returns user's name.

And this is my part of code to check if user already exists in database.

$user_profile = $facebook->api('/me');
$name = $user_profile['name'];
$mysqli = new mysqli("asd", "asdf", "pw", "asdssst");
/* Create the prepared statement */
$stmt = $mysqli->prepare("SELECT COUNT(*) AS num FROM myTable WHERE userName = ?") or die("Prepared Statement Error: %s\n" . $mysqli->error);
/* Bind results to variables */
$stmt->bind_param('s', $name);
/* Execute the prepared Statement */
$stmt->execute();
$data = $stmt->fetch();
if ($data['num'] > 0) {
    echo "bad";
    print "user already exists\n";
} else {
    echo "good";
    $apiResponse = $facebook->api('/me/feed', 'POST', $post_data);
    print "No user in database\n";
}
/* Close the statement */
$stmt->close();

It always return: good No user in database whether user is in database or not. That means $data['num'] is always 0.

P.S. I know that I need to use FB user ID instead of username, but in this case I need to do that.

Related: How to check if a row exists in MySQL?

Dharman
– Dharman ♦

2019-11-27 21:32:25 +00:00
Commented Nov 27, 2019 at 21:32 — Dharman
– Dharman ♦, Commented Nov 27, 2019 at 21:32

Marko · Accepted Answer · 2013-12-12 20:51:53Z

1

I would use something like this

$mysqli = new mysqli('',"","","");
$query = 'SELECT username FROM user WHERE username = ?';
$stmt = $mysqli->prepare($query);
$name = 'asdf';
$stmt->bind_param('s', $name);
$stmt->execute();
$stmt->bind_result($user);
if($stmt->fetch())
   echo 'Username '.$user. ' exists';
else 
  echo 'User doesnt exists';
$stmt->close();

answered Dec 12, 2013 at 20:51

Marko

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9 Comments

user3097011 Over a year ago

Thank you for answer, but in both cases I get User doesnt exists nevermind If user is written to database or not.

user3097011 Over a year ago

Maybe this line is incorrect $stmt->bind_result($user); ? Where It get $user value?

Marko Over a year ago

bind_result is used to bind data into a variable. for example if your query is requesting two parameters like 'SELECT username, password...' then you tell bind_result($user,$password) to save that data into corresponding variables.

user3097011 Over a year ago

But in code I have other variable $user which contains FB user ID

Marko Over a year ago

thats fine. i am using code i have post for my needs and it works, I'm not sure why your doesnt. problem must be somewhere else

|

ChaseC · Accepted Answer · 2013-12-12 21:07:37Z

0

Check if the variable has a result to it. Something like this should work.

//So you have your variable $name here + it returns a value
$name = $user_profile['name'];
//You can put this if statement anywhere below it
if($name > 1){
//log user in
}

edited Dec 12, 2013 at 21:07

answered Dec 12, 2013 at 20:47

ChaseC

4262 gold badges6 silver badges18 bronze badges

5 Comments

user3097011 Over a year ago

Thank you for answer, but I misunderstood where this part of code I need to use?

ChaseC Over a year ago

You need to put this sort of code AFTER you get the results of the query.

user3097011 Over a year ago

Could you update your answer how It looks like in my code, please? Of course If you have time.

user3097011 Over a year ago

Thank you for answer, but what do you mean in this line //log user in what I need to use here? If I use echo $name It successfully returns FB username.

user3097011 Over a year ago

And name is string, how can I check If It is > 0?

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