<?php
$example = "DELIM1test1DELIM2test2DELIM1test3DELIM2test4"; // and so on
$keywords = preg_split("/DELIM1|DELIM2/", $example,0,PREG_SPLIT_NO_EMPTY
);
PD9waHAKJGV4YW1wbGUgPSAiREVMSU0xdGVzdDFERUxJTTJ0ZXN0MkRFTElNMXRlc3QzREVMSU0ydGVzdDQiOyAvLyBhbmQgc28gb24KJGtleXdvcmRzID0gcHJlZ19zcGxpdCgiL0RFTElNMXxERUxJTTIvIiwgJGV4YW1wbGUsMCxQUkVHX1NQTElUX05PX0VNUFRZKTsKcHJpbnRfcigka2V5d29yZHMpOw==