PHP未定义变量在同一函数内

Question

I've been searching for the answer for a while, but no luck: I have defined a variable inside this function and I try to use it in the same function, but PHP gives me this:

Notice:
Undefined variable: query in C:\\xampp\\htdocs\\liquidity\\includes\\layout\\DBBroker.php on line 42 Warning: mysqli_query():
Empty query in C:\\xampp\\htdocs\\liquidity\\includes\\layout\\DBBroker.php on line 42

How is this possible? I define it and use it inside the same function. The function is prikaziClanove, the one with "//here the problem starts" next to it. Code:

<?php
    define ("DBHOST", "localhost");
    define("DBUSER", "standard_user");
    define("DBPASS", "standard");
    define("DBNAME", "liquidity");
    class DBBroker {
        private $dbhost;
        private $dbuser;
        private $dbpass;
        private $dbname;
        private $conn;

        function __construct() { //connects to DB and checks the connection
            $this->dbhost = DBHOST;
            $this->dbuser = DBUSER;
            $this->dbpass = DBPASS;
            $this->dbname = DBNAME;

            $this->conn = mysqli_connect($this->dbhost, $this->dbuser, $this->dbpass, $this->dbname);
            if (!$this->conn) {
                die("Došlo je do greške pri konektovanju na bazu: ".mysqli_error($this->conn));
            }
        }

        /*$conn = mysqli_connect(DBHOST, DBUSER, DBPASS, DBNAME);
        if ($conn) {
            die("Došlo je do greške pri konektovanju na bazu: ".mysqli_error($conn));
        }*/

        function chckResult($rs) { //checks the query result of query, $rs=result
            if (!$rs) {
                echo("Upit nije uspešno izvršen.");
            }
        }

        function closeConnection() { //closes the connection
            mysqli_close($connection);
        }

        function prikaziClanove($username) { //here the problem starts
            $query = "SELECT * FROM clan WHERE username='".$username."';".
            $result = mysqli_query($this->conn, $query);
            $this->chckResult($result);
            echo($result);
        }
    }

?>

Answer 1

If you look at this line:

$query = "SELECT * FROM clan WHERE username='".$username."';".

That's not actually closing the string, it's using the concatenation operator.

Try this instead:

$query = "SELECT * FROM clan WHERE username='".$username."'";