strpos() return value always evaluates as true when compared with !== 0

Question

My code always return "true" whatever the string is I tried a bunch of thing but they are only return false... I have no idea what I can do to fix this... my code:

public function isBlacklisted($string)
{
    $apis = mysql_connect("mysql.hostinger.fr", "mysql user", "testpass") or die(mysql_error());
    mysql_select_db("u770656121_api", $apis);
    $sql = "SELECT * FROM blacklist";
    $result = mysql_query($sql, $apis);
    while($row = mysql_fetch_array($result)) {
        $username = $row['username'];
        if (strpos($string,$username) !== 0) {
            return true;
            break;
        } else {
            return false;
            break;
        }
    }
}

Answer 1

strpos returns false is it is not found, and 0 if it is in the first position of the string. It sounds like you want to do:

if (strpos($string,$username) !== false) {

Also, you are looping over the DB results, you should only return if it is found:

 while($row = mysql_fetch_array($result)) {
    $username = $row['username'];
    if (strpos($string,$username) !== false) {
        return true;
    }
 }
 return false;

Or, even better:

$sql = "SELECT * FROM blacklist WHERE 'username' LIKE '%$username%'";
$result = mysql_query($sql, $apis);
while($row = mysql_fetch_array($result)) {
   if ($row['username']) return true;
}

making sure to escape $username and ideally switching to mysqli or pdo instead of using deprecated mysql statements.