Parse error: syntax error, unexpected '$ch' (T_VARIABLE), expecting ',' or ';' in C:\OSPanel\domains\open-case.ru\admin\create-case.php on line 17

<?
require('../libs/connection.php');
$skins = R::find('skins');
?>
<form action="<? $_SERVER['PHP_SELF'] ?>" method="POST">
    <p><input type="text" name="name" placeholder="Название кейса"></p>
    <? 
    $ch = array();
    $i = 0;
    foreach ($skins as $skin) 
    {
        if($skin['rare'] == "Ширпотреб")
        {
            echo "<input type='checkbox' name="$ch[$i]">" . $skin['gun'] . ' | ' . $skin['name'] . '<br>';
            $i++;
        }
        elseif($skin['rare'] == "Промышленное качество")
        {
            echo "<input type='checkbox' name="$ch[$i]">" . '<font color="0099ff">' . $skin['gun'] . ' | ' . $skin['name'] . '</font> <br>';
            $i++;
        }
        elseif($skin['rare'] == "Армейское качество")
        {
            echo "<input type='checkbox' name="$ch[$i]">" . '<font color="0033cc">' . $skin['gun'] . ' | ' . $skin['name'] . '</font> <br>';
            $i++;
        }
        elseif($skin['rare'] == "Запрещенное")
        {
            echo "<input type='checkbox' name="$ch[$i]">" . '<font color="9900cc">' . $skin['gun'] . ' | ' . $skin['name'] . '</font><br>';
            $i++;
        }
        elseif($skin['rare'] == "Засекреченое")
        {
            echo "<input type='checkbox' name="$ch[$i]">" . '<font color="ff00ff">' . $skin['gun'] . ' | ' . $skin['name'] . '</font> <br>';
            $i++;
        }
        elseif($skin['rare'] == "Тайное")
        {
            echo "<input type='checkbox' name="$ch[$i]">" . '<font color="ff0000">' .$skin['gun'] . ' | ' . $skin['name'] . '</font> <br>';
            $i++;
        }
    }
    if(isset($_POST['create']))
    {
        $case = R::dispense('cases');
        $case->name = $_POST['name'];
        #$case->slot1 = $checkbox['']
    }
    ?>
    <p><input type="submit" name="create" value="Создать кейс"></p>
</form>

Выдает ошибку

Parse error: syntax error, unexpected '$ch' (T_VARIABLE), expecting ',' or ';' in C:\OSPanel\domains\open-case.ru\admin\create-case.php on line 17