- json_encode: documentation ( source)
<?php
$extra = [];
$extra['social_auth'] = [];
$a = [];
$a['login'] = '1234sflfkjasdf';
$a['vterm_id'] = 'VKGolosa';
$extra['social_auth'][] = $a;
echo json_encode(['extra' => $extra], JSON_UNESCAPED_UNICODE);