从特定关键字或位置遍历php

Question

I want to find the string from

$str = "Hello this is dummy.test. in this string  
any character, any special character can appear. it is not a fixed type 
text and predefined. this string will not read manually check by the 
Programmer.Sorry for the bad English.";

my algo is fixed because some kind of problem. First I want to find the position of test keyword then want to go back from test to dummy keyword to find position of dummy keyword .

I also searched and also use the internet but no any function found in PHP which can traverse back in this way.

I also test strrpos() but not relevant and required result. Any solution please.

Output needed : dummy.test

Algo : find first right (test) and then right to left (dummy) only. not first right (test) and then from starting to left (dummy) .

Answer 1

strrpos Would be the right way. If I understand you correctly, this should work, using the offset parameter:

$test = strrpos($str, 'test');
$dummy = strrpos($str, 'dummy', $test);

This will find the last "dummy" that occurs before the last "test".