php regex surround string with parentheses unless already surrounded by non-literal parentheses

I have some code that is augmenting a regular expression by combining horizontal white开发者_Python百科-space and surrounding it in parentheses, unless it is already surrounded by non-backslashed parentheses. I have a piece of code that's working:

$regex_find = preg_replace('/(?<!\()[ \t]{2,}(?!\))/', '([ \t]{2,})', $regex_find);

However, for starters, the look-behind segnment, (?<!\(), should really allow for a literal left parenthesis, \(, but not a stand-alone left parenthesis, (.

Thanks

Your original regex also has another problem. Try running it on this:

 $str = "asdf(     )sdf     sdf";
 //results in: "asdf( (   ) )sdf(     )sdf"

This regex should work:

$regex_find = '(    asdf(     )sdf     sdf';
preg_replace('/(?<!(\(|\s)(?=\s*\)))\s{2,}/','($0)',$regex_find);
//result = "((    )asdf(     )sdf(     )sdf"

Edit: Here is Qtax's solution with the additional lookbehind to ignore escaped \(

/(?<!((?<!\\)\(|\s)(?=\s*\)))\s{2,}/