Regex expression for getting string starting with something and ending with something else

regexForFunctions.php

<?php
//start with $ end with )
preg_match_all('/\$.+?(?=\))/', '<p>$test(hello)</p> <p>$test(testing)</p>', $matches, PREG_UNMATCHED_AS_NULL);
print_r($matches);
/*
Array
(
    [0] => Array
        (
            [0] => $test(hello
            [1] => $test(testing
        )
)
*/
?>