fatal error in php and mysql - php

Question

i am having a problem with my script in php/mysql. here is the error displayed by the server:
Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'if exists (select * from notificacoes where uid in () order by id desc' at line 1' in C:\wamp\www\bigui\classes\Notificacoes.class.php on line 57
and here is my php code:
static function listar(){
$strIdAmigos = Amizade::$strIdAmigos;
$query = self::getConn()->query('select * from notificacoes where uid in ('.$strIdAmigos.') order by id desc');
return $query->fetchAll(PDO::FETCH_ASSOC);
}
my table in the mysql is empty, with no values. when i insert a value in it, the error goes away and everything is fine. any help?

Answer 1

If $strIdAmigos is empty, it causes syntax errors.
Before you execute this query, you should check the $strIdAmigos value whether it's empty or not to avoid this issue. Not to forget to escape the values if needed.

Answer 2

When you run your query with nothing in the variable $strIdAmigos, it will error out.
Try initializing and/or checking your variable, $strIdAmigos, before running your query:
$strIdAmigos = "";
if (empty($strIdAmigos)) {
/* Uh oh, throw an error */
} else {
$query = self::getConn()->query('select * from notificacoes where uid in ('.$strIdAmigos.') order by id desc');
}
Note that if $strIdAmigos = "0" , the empty($strIdAmigos) will still evaluate to true and, hence, will NOT run the query.