Description:
------------
I executed this test script below, redirecting the result to a file, and I got an execution result of "Â".
When I execute it on other regular expression engines like java and python using the same regular expression and string, they both result in "£", unlike PHP. I don't understand why PHP has such a different result, is this a special implementation of the PHP regular expression engine or a defect in the engine?

Test script:
---------------
<?php
function matchTest($reg,$str){
    preg_match($reg,$str,$r);
    if (empty($r)) {
        return "";
    }   
        else{
    return $r[0];
    }
}
$regex = "/[£]/";
$testString = "£";
$result = matchTest($regex, $testString);
print_r($result);
?>

Expected result:
----------------
£

Actual result:
--------------
Â