Handling of parentheses in PHP search [closed]

I have a system that follows the concept of information retrieval of Artificial Intelligence. Example:

ovo // Search all documents that have an egg

not ovo // Search all documents that do not have an egg.

ovo and óleo // Search for all documents that have egg and oil

I'm implementing parenthesis handling, but I'm having difficulty. Example:

ovo and (not óleo)

To remove the parentheses I did:

if ($array[0] == '(')
    $array = substr($array, 1);
if ($array[strlen($array)-1] == ')')
    $array = substr($array, 0, -1);

I have the following functions:

operador_and($array, $array2)
operador_or($array, $array2)
operador_xor($array, $array2)
operador_not($array)

How can I do to select everything inside the parentheses, then do the rest?