$data = array(
    array('title' => 'apple', 'quantity' => 5, 'price' => 1.2),
    array('title' => 'orange', 'quantity' => 3, 'price' => 0.8),
    array('title' => 'banana', 'quantity' => 2, 'price' => 1.5),
    array('title' => 'apple', 'quantity' => 2, 'price' => 1.1),
    array('title' => 'banana', 'quantity' => 1, 'price' => 1.3),
    array('title' => 'orange', 'quantity' => 4, 'price' => 0.9),
);

$sums = array();
foreach ($data as $row) {
    $title = $row['title'];
    if (!isset($sums[$title])) {
        $sums[$title] = array('quantity' => 0, 'price' => 0);
    }
    $sums[$title]['quantity'] += $row['quantity'];
    $sums[$title]['price'] += $row['quantity'] * $row['price'];
}

foreach ($sums as $title => $sum) {
    echo $title . '      ';
    echo 'quantity: ' . $sum['quantity'] . '      ';
    echo 'price: ' . round($sum['price'], 2) . '
';
}

输出结果：

apple     quantity: 7      price: 9.18
orange    quantity: 7      price: 4.9
banana    quantity: 3      price: 4.1