<?php
$re = "/\[(.*)\|(.*)\]/";
$str = "wwetwetw[id1|Павел Дуров]twtweyweywy";
$subst = '<a href="http://content-available-to-author-only.com/$1" target="_blank">$2</a>';
echo $result;
PD9waHAKCiRyZSA9ICIvXFsoLiopXHwoLiopXF0vIjsgCiRzdHIgPSAid3dldHdldHdbaWQxfNCf0LDQstC10Lsg0JTRg9GA0L7Qsl10d3R3ZXl3ZXl3eSI7IAokc3Vic3QgPSAnPGEgaHJlZj0iaHR0cDovL2NvbnRlbnQtYXZhaWxhYmxlLXRvLWF1dGhvci1vbmx5LmNvbS8kMSIgdGFyZ2V0PSJfYmxhbmsiPiQyPC9hPic7IAogCiRyZXN1bHQgPSBwcmVnX3JlcGxhY2UoJHJlLCAkc3Vic3QsICRzdHIpOwplY2hvICRyZXN1bHQ7