коректно решение

<!DOCTYPE html>
<html>
<head>
    <title>Price List</title>
    <meta charset="utf-8" />
</head>
<body>
<form method="get" action="#">
    Price List: <textarea name="priceList" rows="15" cols="120">  <table class="priceListTable">
            <tr> <th>Product</th> <th>Category</th> <th>Price</th> <th>Currency</th></tr>
            <tr> <td>8GB DDR3L 1600 KINGSTON SODIMM</td><td>RAM</td><td>87.00</td>  <td>  USD</td></tr>
            <tr> <td>500GB Toshiba, SATA 6Gb/s, 7200rpm, 32MB</td> <td>HDD</td> <td>18.41</td> <td>BGN </td></tr>
            <tr> <td>AMD A10-5800K X4 3.8GHz, 4MB Cache</td><td>CPU</td>   <td> 186.00</td> <td>BGN </td></tr>
            <tr> <td> SSD 2.5&quot;, 120GB, Corsair F120 LS, SATA3</td> <td> HDD</td> <td> 180.50</td> <td> BGN </td>  </tr>
            <tr> <td>500GB Toshiba, SATA 6Gb/s, 7200rpm, 32MB</td> <td>HDD</td> <td>28.41</td> <td>BGN </td> </tr>
            <tr> <td>ASRock B75M-GL R2.0</td><td>motherboard</td> <td>  47.55</td> <td>EUR</td>  </tr>
            <tr> <td>1TB Toshiba, SATA 6Gb/s, 7200rpm, 32MB</td> <td>HDD</td><td> 52.82 </td> <td>EUR</td></tr>
            <tr> <td>16GB Micro SDHC, A-Data, Class10</td><td>RAM   </td><td>15.03</td><td>BGN</td></tr>
            <tr> <td>500GB Toshiba, SATA 6Gb/s, 7200rpm, 32MB</td> <td>HDD</td> <td>38.41</td> <td>BGN </td>    </tr>
        </table></textarea> <br/>
    <input type="submit" value="Send" />
</form>

<?php
if (!isset($_GET['priceList'])) die;

$input = preg_replace("/\r?\n/m","", $_GET['priceList']);
$input = preg_replace("/<\/tr>/","</tr>\n",$input);
$pattern = "/<tr>\s*<td>(.*?)<\/td>\s*<td>(.*?)<\/td>?\s*<td>(.*?)<\/td>?\s*<td>(.*?)<\/td>?\s*<\/tr>/im";
preg_match_all($pattern,$input,$match,PREG_SET_ORDER);

$obj = [];
for ($i=0; $i<count($match); $i++) {
    $match[$i] = array_map('trim',$match[$i]);
    $arr = ["product"=>html_entity_decode($match[$i][1]), "price"=>$match[$i][3], "currency"=>$match[$i][4], "id"=>$i];

    if (isset($obj[$match[$i][2]])) {
        array_push($obj[$match[$i][2]],$arr);
    } else {
        $obj[$match[$i][2]] = [$arr];
    }
}

function mySort($a, $b) {
    if ($a['product'] == $b['product']) return ($a['id']>$b['id']) ? 1 : -1;
    return ($a['product'] > $b['product']) ? 1 : -1;
}
foreach (array_keys($obj) as $key) {
    uasort($obj[$key],'mySort');
    $obj[$key] = array_values($obj[$key]);
    foreach ($obj[$key] as &$arr) {
        unset($arr['id']);
    }
}
ksort($obj,SORT_ASC);
echo json_encode($obj);