Regex - match an optionally repeated pattern of capture groups

Question

Appologies for not knowing exactly how to word this question. There is probably even a better title. I'm open to suggestions.

I have the following subjects:

(Field1 = 'Value1') and (Field2 = 'Value2')

and

(Field1 = 'Value1') and (Field2 = 'Value2') or (Field3 = 'Value3')

I want to match in such a way that I have each thing between the () in groups and each conjunction in a group. So, for the second one, some variation of

0: Field1 = 'Value1'
1: and
2: Field2 = 'Value2'
3: or
4: Field3 = 'Value3'

The good news is, I've got regex that works on the first:

\(([A-Za-z0-9\s\'=]+)\) (and|or) \(([A-Za-z0-9\s\'=]+)\)

https://regex101.com/r/hMXAXS/1

But (on the second subject) it doesn't match the third "and ()". I need to support arbitrary numbers of groups. I can modify it to just look for "and ()" but then it doesn't match the first group.

How can I tell regex to do this? I either need to "double count" some groups (which is fine) or have some other way of optionally looking for additional patterns and matching them.

Thanks for the help!

PS: I was able to get my application to work with the regex ((and|or) \(([A-Za-z0-9\s\'=]+)\))+ and then just accepting that the first group would never match and creating application logic to support this. Still, I'd bet there's a better way.

Answer 1

If you are OK with getting three groups per match...

1 = key 2 = value 3 = conjunction verb

Then this regex will also allow parenthesis in the value.

/\((.*?) = '(.*?)'\) ?(and|or)?/gm

Which results in these matches for this string...

(Field1 = 'Value1') and (Field2 = '(in parenthesis)') and (Field3 = 'Value3')

Answer 2

You may use preg_match_all here with the regex pattern (?<=\()(.*?)(?=\))|(?:and|or) as follows:

$input = "(Field1 = 'Value1') and (Field2 = 'Value2') or (Field3 = 'Value3')";
preg_match_all("/(?<=\()(.*?)(?=\))|(?:and|or)/", $input, $matches);
print_r($matches[0]);

This prints:

Array
(
    [0] => Field1 = 'Value1'
    [1] => and
    [2] => Field2 = 'Value2'
    [3] => or
    [4] => Field3 = 'Value3'
)

Answer 3

If you are not worried about fringe cases where delimiting words or paretheses can exist within the parenthetical expressions, then preg_split() generates the desired flat array.

Code: (Demo)

$input = "(Field1 = 'Val and ue1') and (Field2 = 'Valu or e2') or (Field3 = 'Value3')";
var_export(
    preg_split(
        "~^\(|\)$|\) (and|or) \(~",
        $input,
        0,
        PREG_SPLIT_NO_EMPTY|PREG_SPLIT_DELIM_CAPTURE
    )
);

Output:

array (
  0 => 'Field1 = \'Val and ue1\'',
  1 => 'and',
  2 => 'Field2 = \'Valu or e2\'',
  3 => 'or',
  4 => 'Field3 = \'Value3\'',
)

Or simplify the pattern by pre-trimming the outermost parentheses. (Demo)

var_export(preg_split("~\) (and|or) \(~", trim($input, '()'), 0, PREG_SPLIT_DELIM_CAPTURE));

---

You can also use the continue metacharacter \G to continue matching from the end of the previous match: (Demo) This takes 88 steps versus Tim's pattern which takes 280 steps to parse the string.

$input = "(Field1 = 'Val and ue1') and (Field2 = 'Valu or e2') or (Field3 = 'Value3')";
preg_match_all('~(?:^\(|\G(?!^)(?:\) | \())\K(?:(?:and|or)|[^)]+)~', $input, $m);
print_r($m[0]);

---

Edit after the asker accepted an answer that does not provide the output array structure stated in the question: (Demo)

preg_match_all("~\((\S+ = '.*?')\) ?(or|and)?~", $input, $m, PREG_SET_ORDER);
print_r($m);

This does not check that a parenthetical expression occurs after a conjunction. Also, when iterating the matches an extra check will be required to see if the third group ([2]) is declared.

Array
(
    [0] => Array
        (
            [0] => (Field1 = 'Val and ue1') and
            [1] => Field1 = 'Val and ue1'
            [2] => and
        )

    [1] => Array
        (
            [0] => (Field2 = 'Valu or e2') or
            [1] => Field2 = 'Valu or e2'
            [2] => or
        )

    [2] => Array
        (
            [0] => (Field3 = 'Value3')
            [1] => Field3 = 'Value3'
        )
)