src/Fixer/FunctionNotation/MethodArgumentSpaceFixer.php
private function fixSpace2(Tokens $tokens, $index)
    {
        // remove space before comma if exist
        if ($tokens[$index - 1]->isWhitespace()) {
            $prevIndex = $tokens->getPrevNonWhitespace($index - 1);

            if (!$tokens[$prevIndex]->equalsAny([',', [T_END_HEREDOC]]) && !$tokens[$prevIndex]->isComment()) {
                $tokens->clearAt($index - 1);
            }
        }

        $nextIndex = $index + 1;
        $nextToken = $tokens[$nextIndex];

        // Two cases for fix space after comma (exclude multiline comments)
        //  1) multiple spaces after comma
        //  2) no space after comma
        if ($nextToken->isWhitespace()) {
            $newContent = $nextToken->getContent();

            if ('ensure_single_line' === $this->configuration['on_multiline']) {
                $newContent = Preg::replace('/\R/', '', $newContent);
            }

            if (
                (!$this->configuration['keep_multiple_spaces_after_comma'] || Preg::match('/\R/', $newContent))
                && !$this->isCommentLastLineToken($tokens, $index + 2)
            ) {
                $newContent = ltrim($newContent, " \t");
            }

            $tokens[$nextIndex] = new Token([T_WHITESPACE, '' === $newContent ? ' ' : $newContent]);

            return;
        }

        if (!$this->isCommentLastLineToken($tokens, $index + 1)) {
            $tokens->insertAt($index + 1, new Token([T_WHITESPACE, ' ']));
        }
    }
private function fixSpace2(Tokens $tokens, $index)
    {
        // remove space before comma if exist
        if ($tokens[$index - 1]->isWhitespace()) {
            $prevIndex = $tokens->getPrevNonWhitespace($index - 1);

            if (!$tokens[$prevIndex]->equalsAny([',', [T_END_HEREDOC]]) && !$tokens[$prevIndex]->isComment()) {
                $tokens->clearAt($index - 1);
            }
        }

        $nextIndex = $index + 1;
        $nextToken = $tokens[$nextIndex];

        // Two cases for fix space after comma (exclude multiline comments)
        //  1) multiple spaces after comma
        //  2) no space after comma
        if ($nextToken->isWhitespace()) {
            $newContent = $nextToken->getContent();

            if ('ensure_single_line' === $this->configuration['on_multiline']) {
                $newContent = Preg::replace('/\R/', '', $newContent);
            }

            if (
                (!$this->configuration['keep_multiple_spaces_after_comma'] || Preg::match('/\R/', $newContent))
                && !$this->isCommentLastLineToken($tokens, $index + 2)
            ) {
                $newContent = ltrim($newContent, " \t");
            }

            $tokens[$nextIndex] = new Token([T_WHITESPACE, '' === $newContent ? ' ' : $newContent]);

            return;
        }

        if (!$this->isCommentLastLineToken($tokens, $index + 1)) {
            $tokens->insertAt($index + 1, new Token([T_WHITESPACE, ' ']));
        }
    }
Method to insert space after comma and remove space before comma.

@param Tokens $tokens
@param int    $index