Split string by spaces and between whole words or individual symbols

I am looking for a regular expression that would also identify and separate commas, the equal sign and any other special characters that I might need in the input.

Right now what I have is $content = preg_split('/[\s]+/', $file_content, -1, PREG_SPLIT_NO_EMPTY);

Which stores the content of the input file into an array where each element is separated by blank spaces.

However for example for function a (int i) {}; the array would look like this:

[0] = function
[1] = a
[2] = (int
[3] = i)
[4] = {};

And what I'd like to achieve with the regular expression is this:

[0] = function
[1] = a
[2] = (
[3] = int
[4] = i
[5] = )
[6] = {
[7] = }
[8] = ;

Use preg_split function with PREG_SPLIT_DELIM_CAPTURE flag:

PREG_SPLIT_DELIM_CAPTURE

If this flag is set, parenthesized expression
in the delimiter pattern will be captured and returned as well.

$input = 'function a (int i) {};';
$content = preg_split('/([\p{P}\p{S}])|\s/', $input,
           -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);

print_r($content);

The output:

Array
(
    [0] => function
    [1] => a
    [2] => (
    [3] => int
    [4] => i
    [5] => )
    [6] => {
    [7] => }
    [8] => ;
)