<?php
$arr=array("I used to live in <Location>London</Location>.", "I work for <Organization> Microsoft Tech.</Organization>
which is in <Location>London</Location>");
foreach ($arr as $str) {
preg_match('/(?:[<>\/\w]+\s*){4}(?=<Location>)/s', $str, $m ); }
?>
PD9waHAKCgokYXJyPWFycmF5KCJJIHVzZWQgdG8gbGl2ZSBpbiA8TG9jYXRpb24+TG9uZG9uPC9Mb2NhdGlvbj4uIiwKICJJIHdvcmsgZm9yIDxPcmdhbml6YXRpb24+IE1pY3Jvc29mdCBUZWNoLjwvT3JnYW5pemF0aW9uPgp3aGljaCBpcyBpbiA8TG9jYXRpb24+TG9uZG9uPC9Mb2NhdGlvbj4iKTsKCmZvcmVhY2ggKCRhcnIgYXMgJHN0cikgewogICBwcmVnX21hdGNoKCcvKD86Wzw+XC9cd10rXHMqKXs0fSg/PTxMb2NhdGlvbj4pL3MnLCAkc3RyLCAkbSApOwogICB2YXJfZHVtcCgkbVswXSk7Cn0KPz4=