Check if username exists using PHP PDO

Question

How do I check if a username exists using PDO? All I need to know is a bool true (exists) or false (does not). I have the initial parts set up but am unsure what to do next

$sthandler = $dbhandler->prepare('SELECT username FROM userdb WHERE username=? LIMIT 1');
$sthandler->execute(array('username'));
// ... What's next?

You are gonna want to count the amount of rows that come up from the query (check tom's answer). If it's 0 the user doesn't exist, if it's 1 or more he does. One tip: I usually don't limit the query, If the username were to exist more then once I can throw an error, this means that something is bugged or a possible intruder duplicated the account... — HTDutchy
– HTDutchy, Commented Nov 29, 2011 at 18:39
@s4uadmin - You have to enforce certain amount of data integrity right in the database, e.g. with a unique index. Otherwise you'll get crazy testing for all the possibilities of corrupted data. — Álvaro González
– Álvaro González, Commented Nov 29, 2011 at 18:53

elitalon · Accepted Answer · 2011-11-29 20:09:58Z

9

Check for the row count:

if ( $sthandler->rowCount() > 0 ) {
  // do something here
}

edited Nov 29, 2011 at 20:09

elitalon

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answered Nov 29, 2011 at 18:32

Tom van der Woerdt

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2 Comments

enchance Over a year ago

Thanks, man. Just what I needed. Final code: if(!$sthandler->rowCount()) throw new invalidUserException();

Brownman Revival Over a year ago

i have a question please enlighten me for example no record exist count will be 0 0 not greater than 0 so nothing will happend should it be $sthandler->rowCount() < 1 so when a user exist it will not do anything to avoid duplicate and if none exist it will proceed?

Álvaro González · Accepted Answer · 2011-11-29 18:38:26Z

2

Just grab the row:

if( $row = $sthandler->fetch() ){
    // User exists: read its details here
}else{
    // User does not exist
}

answered Nov 29, 2011 at 18:38

Álvaro González

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Comments

Geert · Accepted Answer · 2011-11-29 18:44:33Z

2

$username_exists = (bool) $sthandler->fetchColumn();

Note that you can even optimize the query a tiny bit since actually you don't need to select the username.

SELECT username FROM userdb ...

becomes

SELECT 1 FROM userdb ...

edited Nov 29, 2011 at 18:44

answered Nov 29, 2011 at 18:38

Geert

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