foreach() 提供的参数无效

Question

I have this code that works for my friend but when I run it, it gave this Warning: Invalid argument supplied for foreach() in C:\wamp64\www\DVD_show.php on line 10

What is the problem?

    '''
    <?php
    try {
        /*** connect to SQLite database ***/
        $dbh = new PDO("sqlite:dvd.db");
    //echo("ok");
    if(isset($_GET['name'])){
    $name=$_GET['name'];
    $sql = "SELECT * FROM DVD where name='".$name."'";
    }else $sql = "SELECT * FROM DVD";
        foreach ($dbh->query($sql) as $row)
            {
            print 'dvds[index++]="#'.$row['name'] ."#".$row['director']. "#".                 $row['price']."#".$row['stock'].'#";<br>';
            //dvds[index++]="#Life is Beautiful#dvd1#10.5#10#history#Roberto Benigni#";
            }
    
        /*** close the database connection ***/
        $dbh = null;
        }
    catch(PDOException $e)
        {
        echo $e->getMessage();
        }
    ?>
    <form action="http://127.0.0.1/DVD_show.php" method="get">
     <p>Please input DVD name: <input type="text" name="name" /></p>
    
     <p><input type="submit" /></p>
    </form>
    '''

Answer 1

$dbh->query($sql) will return you Statement . You should use fetch or fetchAll to get the results. While fetch will return only one - so not iterable, you should use fetchAll , which always returns array.

Answer 2

The dbh-> query is wrong at this place as it only returns a statment but not something you can use with foreach

You first need to use the fetch() or fetchAll() methods

Please see changed code.

NOTE: If you have a HIGH number of results it is not recommended to use fetchAll as it loads the wohle dataset. then better use fetch() and while like shown in the example ar the link below.

  <?php
    try {
        /*** connect to SQLite database ***/
        $dbh = new PDO("sqlite:dvd.db");
    //echo("ok");
    if(isset($_GET['name'])){
    $name=$_GET['name'];
    $sql = "SELECT * FROM DVD where name='".$name."'";
    }else $sql = "SELECT * FROM DVD";
    
//change this 
    
$data =  $dbh->query($sql) ->fetchAll();
        foreach ($data as $row)

//changes end 
            {
            print 'dvds[index++]="#'.$row['name'] ."#".$row['director']. "#".                 $row['price']."#".$row['stock'].'#";<br>';
            //dvds[index++]="#Life is Beautiful#dvd1#10.5#10#history#Roberto Benigni#";
            }

        /*** close the database connection ***/
        $dbh = null;
        }
    catch(PDOException $e)
        {
        echo $e->getMessage();
        }
    ?>
    <form action="http://127.0.0.1/DVD_show.php" method="get">
     <p>Please input DVD name: <input type="text" name="name" /></p>

     <p><input type="submit" /></p>
    </form>
    '''

please see:

https://phpdelusions.net/pdo_examples/select