src/Tokenizer/TokensAnalyzer.php
public function isUnaryPredecessorOperator($index)
    {
        static $potentialSuccessorOperator = [T_INC, T_DEC];

        static $potentialBinaryOperator = ['+', '-', '&', [CT::T_RETURN_REF]];

        static $otherOperators;
        if (null === $otherOperators) {
            $otherOperators = ['!', '~', '@', [T_ELLIPSIS]];
        }

        static $disallowedPrevTokens;
        if (null === $disallowedPrevTokens) {
            $disallowedPrevTokens = [
                ']',
                '}',
                ')',
                '"',
                '`',
                [CT::T_ARRAY_SQUARE_BRACE_CLOSE],
                [CT::T_DYNAMIC_PROP_BRACE_CLOSE],
                [CT::T_DYNAMIC_VAR_BRACE_CLOSE],
                [T_CLASS_C],
                [T_CONSTANT_ENCAPSED_STRING],
                [T_DEC],
                [T_DIR],
                [T_DNUMBER],
                [T_FILE],
                [T_FUNC_C],
                [T_INC],
                [T_LINE],
                [T_LNUMBER],
                [T_METHOD_C],
                [T_NS_C],
                [T_STRING],
                [T_TRAIT_C],
                [T_VARIABLE],
            ];
        }

        $tokens = $this->tokens;
        $token = $tokens[$index];

        if ($token->isGivenKind($potentialSuccessorOperator)) {
            return !$this->isUnarySuccessorOperator($index);
        }

        if ($token->equalsAny($otherOperators)) {
            return true;
        }

        if (!$token->equalsAny($potentialBinaryOperator)) {
            return false;
        }

        $prevToken = $tokens[$tokens->getPrevMeaningfulToken($index)];

        if (!$prevToken->equalsAny($disallowedPrevTokens)) {
            return true;
        }

        if (!$token->equals('&') || !$prevToken->isGivenKind(T_STRING)) {
            return false;
        }

        static $searchTokens = [
            ';',
            '{',
            '}',
            [T_FUNCTION],
            [T_OPEN_TAG],
            [T_OPEN_TAG_WITH_ECHO],
        ];
        $prevToken = $tokens[$tokens->getPrevTokenOfKind($index, $searchTokens)];

        return $prevToken->isGivenKind(T_FUNCTION);
    }
public function isUnaryPredecessorOperator($index)
    {
        static $potentialSuccessorOperator = [T_INC, T_DEC];

        static $potentialBinaryOperator = ['+', '-', '&', [CT::T_RETURN_REF]];

        static $otherOperators;
        if (null === $otherOperators) {
            $otherOperators = ['!', '~', '@', [T_ELLIPSIS]];
        }

        static $disallowedPrevTokens;
        if (null === $disallowedPrevTokens) {
            $disallowedPrevTokens = [
                ']',
                '}',
                ')',
                '"',
                '`',
                [CT::T_ARRAY_SQUARE_BRACE_CLOSE],
                [CT::T_DYNAMIC_PROP_BRACE_CLOSE],
                [CT::T_DYNAMIC_VAR_BRACE_CLOSE],
                [T_CLASS_C],
                [T_CONSTANT_ENCAPSED_STRING],
                [T_DEC],
                [T_DIR],
                [T_DNUMBER],
                [T_FILE],
                [T_FUNC_C],
                [T_INC],
                [T_LINE],
                [T_LNUMBER],
                [T_METHOD_C],
                [T_NS_C],
                [T_STRING],
                [T_TRAIT_C],
                [T_VARIABLE],
            ];
        }

        $tokens = $this->tokens;
        $token = $tokens[$index];

        if ($token->isGivenKind($potentialSuccessorOperator)) {
            return !$this->isUnarySuccessorOperator($index);
        }

        if ($token->equalsAny($otherOperators)) {
            return true;
        }

        if (!$token->equalsAny($potentialBinaryOperator)) {
            return false;
        }

        $prevToken = $tokens[$tokens->getPrevMeaningfulToken($index)];

        if (!$prevToken->equalsAny($disallowedPrevTokens)) {
            return true;
        }

        if (!$token->equals('&') || !$prevToken->isGivenKind(T_STRING)) {
            return false;
        }

        static $searchTokens = [
            ';',
            '{',
            '}',
            [T_FUNCTION],
            [T_OPEN_TAG],
            [T_OPEN_TAG_WITH_ECHO],
        ];
        $prevToken = $tokens[$tokens->getPrevTokenOfKind($index, $searchTokens)];

        return $prevToken->isGivenKind(T_FUNCTION);
    }
Checks if there is an unary predecessor operator under given index.

@param int $index

@return bool