where子句变量发生故障

Question

I am new to oop environment and there is something that seems to be not right here, I have searched all over but the ones available is the query string is given inside the class.

if(isset($_POST['search'])){
    include('../Classes/class.config.php');
    include('../Classes/class.dbActions.php');
    $execute=new execute();
    $execute->select('SELECT * FROM users where username="'.$_POST['search'].'" ');
    $array=$execute->Fetch();
    echo $array['chasisNo'].'<br/>';
}

when I change:

$execute->select('SELECT * FROM users where username="'.$_POST['search'].'" ');

to this

$execute->select('SELECT * FROM users '); 

It works perfectly by listing the top
Now what's wrong with this code in that even if i pass a string like

$execute->select('SELECT * FROM users where username="oketch" ');

it does not work

here is the execute class

class execute extends db
{
    private $sqlString;
    private $selected;
    private $querySelected;
    public function select($sqlString)
    {
        $connection=$this->getConnection();
        $this->querySelected=$connection->query($sqlString);
        if($this->querySelected->num_rows>0) {
            $this->Fetch();
        }
        else {
            echo'No Data Available';
        }   
    }   

    public function Fetch() {
        return $this->querySelected->fetch_array();
    }

Answer 1

You're doing a $this->Fetch(); inside select() . I assume this fetches one row of the result set. You then do a subsequent $execute->Fetch() to actually get the result you're looking for.

Without a WHERE clause, there will likely be multiple rows. The first result row is consumed and goes into the aether by the Fetch() inside select() . You then retrieve the second row and display it.
With a WHERE clause there's only one row which is consumed into the aether, and then there's no actual row left to fetch and display.