我对使用迭代的while循环有点困惑..像这样使用它，更干净..正确地获取所有行^_^

$result = $dbc->query("SELECT * FROM shop");
while($row = $result->fetch_assoc()){
    echo "$row['item_name']";
}

我修好了。这是密码。

<?php # DISPLAY COMPLETE PRODUCTS PAGE.

# Access session.

session_start() ;

# Redirect if not logged in.

if ( !isset( $_SESSION[ 'user_id' ] ) ) { require ( 'login_tools.php' ) ; load() ; }

# Set page title and display header section.

$page_title = 'Shop' ;
include ( 'includes/header.html' ) ;

# Open database connection.

require ( '..\connect_db.php' ) ;

# Retrieve items from 'shop' database table.

$q = "SELECT * FROM shop " ;
$r = mysqli_query( $dbc, $q ) ;
if ( mysqli_num_rows( $r ) > 0 )
{
    #<a href='page2.php?id=2489&user=tom'>link to page2</a>

  # Display body section.
  echo '<UL>
            <li><a href="shop_details.php?id=1">View Item</a></li>
            <li><a href="shop_details.php?id=2">View Item</a></li>          
            <li><a href="shop_details.php?id=3">View Item</a></li>
        </UL>
        ';

    #Displays every item in the store. 
  echo '<table><tr>';

    $formatting = 1;
   while ( $row = mysqli_fetch_array( $r, MYSQLI_ASSOC ))
  {
      echo $formatting;
    if ($formatting == 5){
    echo '<td width=20%><strong>' . $row['item_name'] .'</strong><br><span style="font-size:smaller">'. 
    $row['item_desc'] . '</span><br><img src='. $row['item_img'].' height=200px><br>$' . $row['item_price'] . 
    '<br><a href="shop_details.php?id='.$row['item_id'].'">View Item</a></td></tr>';
    $formatting = 1;
    }
    else 
    {
        echo $formatting;
       echo '<td><strong>' . $row['item_name'] .'</strong><br><span style="font-size:smaller">'. 
    $row['item_desc'] . '</span><br><img src='. $row['item_img'].' height=200px><br>$' . $row['item_price'] . 
    '<br><a href="shop_details.php?id='.$row['item_id'].'">View Item</a></td>';
    $formatting ++;
    }
  }

  echo '</table>';

  # Close database connection.
  mysqli_close( $dbc ) ; 
}

# Or display message.

else { echo '<p>There are currently no items in this shop.</p>' ; }

# Create navigation links.

echo '<p><a href="cart.php">View Cart</a> | <a href="forum.php">Forum</a> | <a href="home.php">Home</a> | <a href="goodbye.php">Logout</a></p>' ;

# Display footer section.

include ( 'includes/footer.html' ) ;

?>

简短的是：

echo '<table><tr>';

$formatting = 0;

while ( $row = mysqli_fetch_array( $r, MYSQLI_ASSOC )) {

    echo '<td><strong>' . $row['item_name'] .'</strong><br><span     style="font-size:smaller">'. 
$row['item_desc'] . '</span><br><img src='. $row['item_img'].' height=200px><br>$' . $row['item_price'] . 
'<br><a href="shop_details.php?id='.$row['item_id'].'">View Item</a></td></tr><tr>';

    if ($formatting == 6) {
        $formatting = 0;
        echo '</tr><tr>';
    }

    $formatting++;
}

echo '</tr></table>';