I'm working on a regex in PHP that will match all inside a parenthesis, I'm having problem with special characters particullarly the ampersand(&) 

If the string inside the parenthesis contains an ampersand it doesn't match.

Here is the sample string 

```
_categories=true(test_asda=asd asdasd,asdawqe&hello=asdads)

```

Here is the expected output

```
test_asda=asd asdasd,asdawqe&hello=asdads

```

Here is the regex I'm currently using

```
/\(([^\&)]+)\)/

```