- print_r: documentation ( source)
- preg_match_all: documentation ( source)
<?php
$str = 'thisip4:isatextexample&ineed.thistext&TXT:&andthis.idontneed&txt:&test.thistext&';
if (preg_match_all('~&([^&]*?thistext[^&]*)&~', $str, $m)) {
print_r($m[1]);
}