Error: Object of class stdClass could not be converted to string

private function _getData() {
$embed = $this->embed;
$embeds = $this->embeds;
if ($embed || $embeds) {
// sort embeds by key first before adding the main embed so it doesn't change the order
ksort($embeds);
if ($embed) array_splice($embeds, $this->_offsetIndex, 0, [$embed]);
}
$data = [
"content" => $this->content,
"username" => $this->username,
"avatar_url" => $this->avatarUrl,
"tts" => $this->tts,
"allowed_mentions" => $this->allowedMentions,
"flags" => $this->flags,
"embeds" => $embeds,
"attachments" => $this->attachments,
"thread_name" => $this->threadName,
];
return json_encode($data);
}

PHP

  private function _getData() {

    $embed = $this->embed;

    $embeds = $this->embeds;

    if ($embed || $embeds) {

      // sort embeds by key first before adding the main embed so it doesn't change the order

      ksort($embeds);

      if ($embed) array_splice($embeds, $this->_offsetIndex, 0, [$embed]);

    }

    $data = [

      "content" => $this->content,

      "username" => $this->username,

      "avatar_url" => $this->avatarUrl,

      "tts" => $this->tts,

      "allowed_mentions" => $this->allowedMentions,

      "flags" => $this->flags,

      "embeds" => $embeds,

      "attachments" => $this->attachments,

      "thread_name" => $this->threadName,

    ];

    return json_encode($data);

  }

Вот эта строка return json_encode($data); еррорит