当Echo不存在时，PHP服务器错误500

当我在某个位置添加echo时，我的php代码运行良好，但当我删除简单的echo "hello";行时，它不会加载php页面，只显示服务器错误500。

以下代码有效：

require 'steam.php';
    $steam = new steam();
    $api = "FC1D74A835829EB99A571235A499638A";
    $query = 'ari9';
    $communityID            =   $steam->getID($query, $api);
    $userInfo               =   $steam->getUserInfo($communityID, $api);
    echo "hello";
    $info = array(
        'communityID'   =>  $communityID,
        'steamID'       =>  $steam->$convertToSteamID($communityID),
        'personaname'   =>  $userInfo['personaname'],
        'profileurl'    =>  $userInfo['profileurl'],
        'lastlogoff'    =>  $userInfo['lastlogoff'],
    );
    foreach ($info as $key => $value) {
        if (strlen($value)===0) {
            $info[$key] = false;
        }
        echo $key." -> ".$value."<br>";
    }
    echo json_encode($info);

并且以下代码不起作用：

require 'steam.php';
    $steam = new steam();
    $api = "FC1D74A835829EB99A571235A499638A";
    $query = 'ari9';
    $communityID            =   $steam->getID($query, $api);
    $userInfo               =   $steam->getUserInfo($communityID, $api);
    $info = array(
        'communityID'   =>  $communityID,
        'steamID'       =>  $steam->$convertToSteamID($communityID),
        'personaname'   =>  $userInfo['personaname'],
        'profileurl'    =>  $userInfo['profileurl'],
        'lastlogoff'    =>  $userInfo['lastlogoff'],
    );
    foreach ($info as $key => $value) {
        if (strlen($value)===0) {
            $info[$key] = false;
        }
        echo $key." -> ".$value."<br>";
    }
    echo json_encode($info);

并且以下代码不起作用：

require 'steam.php';
    $steam = new steam();
    $api = "FC1D74A835829EB99A571235A499638A";
    $query = 'ari9';
    $communityID            =   $steam->getID($query, $api);
    $userInfo               =   $steam->getUserInfo($communityID, $api);
    $info = array(
        'communityID'   =>  $communityID,
        'steamID'       =>  $steam->$convertToSteamID($communityID),
        'personaname'   =>  $userInfo['personaname'],
        'profileurl'    =>  $userInfo['profileurl'],
        'lastlogoff'    =>  $userInfo['lastlogoff'],
    );
    foreach ($info as $key => $value) {
        if (strlen($value)===0) {
            $info[$key] = false;
        }
        echo $key." -> ".$value."<br>";
    }
    echo json_encode($info);
    echo "Hello";

第一段代码具有第9行上的回波，第二段代码与第一段代码相同，只是去除了第9行的回波。我对此感到困惑。