when migrating a function from javascript to php and given the same input data the results are different

Question

I am trying to convert a function written in Javascript to PHP, but even though it is written the same and receiving the same input data it returns different results.

A little context. I am working on creating play days for a tournament in a dynamic way. The input data represents the clashes that will take place between the teams throughout the tournament

Thus

Given the following data

combinations = [
  [ 'A', 'B' ], [ 'A', 'C' ],
  [ 'A', 'D' ], [ 'B', 'C' ],
  [ 'B', 'D' ], [ 'C', 'D' ],
  [ 'C', 'D' ], [ 'B', 'D' ],
  [ 'B', 'C' ], [ 'A', 'D' ],
  [ 'A', 'C' ], [ 'A', 'B' ],
  [ 'A', 'B' ], [ 'A', 'C' ],
  [ 'A', 'D' ], [ 'B', 'C' ],
  [ 'B', 'D' ], [ 'C', 'D' ]
]

Javascript

const getMatches = (combinations) => {
  let matches = [];
  let i = 0;

  while (combinations.length) {
    for (const [index, combination] of combinations.entries()) {
      if (combinations.length === 1) {
        matches[i - 1].push(combination);
        combinations.splice(index, 1);
        break;
      }

      if (index === 0) {
        matches.push([combination]);

        combinations.splice(index, 1);
        continue;
      }

      const [team1, team2] = combination;
      const idx = matches[i].findIndex((match) => {
        return match.includes(team1) || match.includes(team2);
      });

      if (idx !== -1) {
        continue;
      }

      matches[i].push(combination);
      combinations.splice(index, 1);
    }

    i++;
  }

  return matches;
};

PHP

function get_matches ($combinations) {
    $matches = [];
    $i = 0;

    while (count($combinations)) {
        foreach ($combinations as $index => $combination) {
            if (count($combinations) === 1) {
                array_push($matches[$i - 1], $combination);
                array_splice($combinations, $index, 1);

                break;
            }

            if ($index === 0) {
                array_push($matches, [$combination]);
                array_splice($combinations, $index, 1);

                continue;
            }

            $idx = find_index($matches[$i], $combination);

            if ($idx !== -1) {
                continue;
            }

            array_push($matches[$i], $combination);
            array_splice($combinations, $index, 1);
        }

        $i++;
    }

    return $matches;
}

Helper function in PHP

function find_index ( $matches, $teams ) {
    [$team1, $team2] = $teams;

    foreach ( $matches as $index => $match ) {
        if (in_array($team1, $match) || in_array($team2, $match)) {
            return $index;
        }
    }

    return -1;
}

Expected output, I am getting this in Javascript

[
  [ [ 'A', 'B' ], [ 'C', 'D' ] ],
  [ [ 'A', 'C' ], [ 'B', 'D' ] ],
  [ [ 'A', 'D' ], [ 'B', 'C' ] ],
  [ [ 'B', 'C' ], [ 'A', 'D' ] ],
  [ [ 'C', 'D' ], [ 'A', 'B' ] ],
  [ [ 'B', 'D' ], [ 'A', 'C' ] ],
  [ [ 'A', 'C' ], [ 'B', 'D' ] ],
  [ [ 'A', 'B' ], [ 'C', 'D' ] ],
  [ [ 'A', 'D' ], [ 'B', 'C' ] ]
]

PHP output

[
  [["A","B"],["C","D"]],
  [["A","C"],["B","D"]],
  [["A","D"],["B","C"]],
  [["B","C"],["A","D"]],
  [["B","D"],["A","C"]],
  [["B","C"],["A","D"]],
  [["A","D"],["B","C"]],
  [["A","B"],["C","D"]],
  [["A","C"],["C","D"]],
  [["B","C"],["C","D"]]
]

The result of PHP has the following errors, first instead of returning an array of 9 items it returns 10, second in item 10 and 9 the team C would play twice at the same time

update 0

The logic of the function is implemented following the advice in this answer, specifically paragraphs 1 to 4

Thanks in advance for the time