src/Fixer/StringNotation/EscapeImplicitBackslashesFixer.php
protected function applyFix(\SplFileInfo $file, Tokens $tokens)
    {
        static $singleQuotedRegex = '/(?<!\\\\)\\\\((?:\\\\\\\\)*)(?![\\\'\\\\])/';
        static $doubleQuotedRegex = '/(?<!\\\\)\\\\((?:\\\\\\\\)*)(?![efnrtv$"\\\\0-7]|x[0-9A-Fa-f]|u{)/';
        static $heredocSyntaxRegex = '/(?<!\\\\)\\\\((?:\\\\\\\\)*)(?![efnrtv$\\\\0-7]|x[0-9A-Fa-f]|u{)/';

        $doubleQuoteOpened = false;
        foreach ($tokens as $index => $token) {
            $content = $token->getContent();
            if ($token->equalsAny(['"', 'b"', 'B"'])) {
                $doubleQuoteOpened = !$doubleQuoteOpened;
            }
            if (!$token->isGivenKind([T_ENCAPSED_AND_WHITESPACE, T_CONSTANT_ENCAPSED_STRING]) || false === strpos($content, '\\')) {
                continue;
            }

            // Nowdoc syntax
            if ($token->isGivenKind(T_ENCAPSED_AND_WHITESPACE) && '\'' === substr(rtrim($tokens[$index - 1]->getContent()), -1)) {
                continue;
            }

            $firstTwoCharacters = strtolower(substr($content, 0, 2));
            $isSingleQuotedString = $token->isGivenKind(T_CONSTANT_ENCAPSED_STRING) && ('\'' === $content[0] || 'b\'' === $firstTwoCharacters);
            $isDoubleQuotedString =
                ($token->isGivenKind(T_CONSTANT_ENCAPSED_STRING) && ('"' === $content[0] || 'b"' === $firstTwoCharacters))
                || ($token->isGivenKind(T_ENCAPSED_AND_WHITESPACE) && $doubleQuoteOpened)
            ;
            $isHeredocSyntax = !$isSingleQuotedString && !$isDoubleQuotedString;
            if (
                (false === $this->configuration['single_quoted'] && $isSingleQuotedString)
                || (false === $this->configuration['double_quoted'] && $isDoubleQuotedString)
                || (false === $this->configuration['heredoc_syntax'] && $isHeredocSyntax)
            ) {
                continue;
            }

            $regex = $heredocSyntaxRegex;
            if ($isSingleQuotedString) {
                $regex = $singleQuotedRegex;
            } elseif ($isDoubleQuotedString) {
                $regex = $doubleQuotedRegex;
            }

            $newContent = Preg::replace($regex, '\\\\\\\\$1', $content);
            if ($newContent !== $content) {
                $tokens[$index] = new Token([$token->getId(), $newContent]);
            }
        }
    }
protected function applyFix(\SplFileInfo $file, Tokens $tokens)
    {
        static $singleQuotedRegex = '/(?<!\\\\)\\\\((?:\\\\\\\\)*)(?![\\\'\\\\])/';
        static $doubleQuotedRegex = '/(?<!\\\\)\\\\((?:\\\\\\\\)*)(?![efnrtv$"\\\\0-7]|x[0-9A-Fa-f]|u{)/';
        static $heredocSyntaxRegex = '/(?<!\\\\)\\\\((?:\\\\\\\\)*)(?![efnrtv$\\\\0-7]|x[0-9A-Fa-f]|u{)/';

        $doubleQuoteOpened = false;
        foreach ($tokens as $index => $token) {
            $content = $token->getContent();
            if ($token->equalsAny(['"', 'b"', 'B"'])) {
                $doubleQuoteOpened = !$doubleQuoteOpened;
            }
            if (!$token->isGivenKind([T_ENCAPSED_AND_WHITESPACE, T_CONSTANT_ENCAPSED_STRING]) || false === strpos($content, '\\')) {
                continue;
            }

            // Nowdoc syntax
            if ($token->isGivenKind(T_ENCAPSED_AND_WHITESPACE) && '\'' === substr(rtrim($tokens[$index - 1]->getContent()), -1)) {
                continue;
            }

            $firstTwoCharacters = strtolower(substr($content, 0, 2));
            $isSingleQuotedString = $token->isGivenKind(T_CONSTANT_ENCAPSED_STRING) && ('\'' === $content[0] || 'b\'' === $firstTwoCharacters);
            $isDoubleQuotedString =
                ($token->isGivenKind(T_CONSTANT_ENCAPSED_STRING) && ('"' === $content[0] || 'b"' === $firstTwoCharacters))
                || ($token->isGivenKind(T_ENCAPSED_AND_WHITESPACE) && $doubleQuoteOpened)
            ;
            $isHeredocSyntax = !$isSingleQuotedString && !$isDoubleQuotedString;
            if (
                (false === $this->configuration['single_quoted'] && $isSingleQuotedString)
                || (false === $this->configuration['double_quoted'] && $isDoubleQuotedString)
                || (false === $this->configuration['heredoc_syntax'] && $isHeredocSyntax)
            ) {
                continue;
            }

            $regex = $heredocSyntaxRegex;
            if ($isSingleQuotedString) {
                $regex = $singleQuotedRegex;
            } elseif ($isDoubleQuotedString) {
                $regex = $doubleQuotedRegex;
            }

            $newContent = Preg::replace($regex, '\\\\\\\\$1', $content);
            if ($newContent !== $content) {
                $tokens[$index] = new Token([$token->getId(), $newContent]);
            }
        }
    }
{@inheritdoc}