$data = 'event: tool_call
data: %7B%22type%22%3A%22function%22%2C%22name%22%3A%22queryKnowledgeBase%22%2C%22arguments%22%3A%22%7B%7D%22%7D
event: answer
data: %D0%94
event: answer
data: %D0%BB%D1%8F';
preg_match_all('~event:(.*?)\n~is', $data, $matches);
echo '<pre>', print_r($matches[1]), '</pre>';