Gajus\Dindent\Indenter::indent PHP Method

    public function indent($input)
    {
        $this->log = array();
        // Dindent does not indent <script> body. Instead, it temporary removes it from the code, indents the input, and restores the script body.
        if (preg_match_all('/<script\\b[^>]*>([\\s\\S]*?)<\\/script>/mi', $input, $matches)) {
            $this->temporary_replacements_script = $matches[0];
            foreach ($matches[0] as $i => $match) {
                $input = str_replace($match, '<script>' . ($i + 1) . '</script>', $input);
            }
        }
        // Removing double whitespaces to make the source code easier to read.
        // With exception of <pre>/ CSS white-space changing the default behaviour, double whitespace is meaningless in HTML output.
        // This reason alone is sufficient not to use Dindent in production.
        $input = str_replace("\t", '', $input);
        $input = preg_replace('/\\s{2,}/', ' ', $input);
        // Remove inline elements and replace them with text entities.
        if (preg_match_all('/<(' . implode('|', $this->inline_elements) . ')[^>]*>(?:[^<]*)<\\/\\1>/', $input, $matches)) {
            $this->temporary_replacements_inline = $matches[0];
            foreach ($matches[0] as $i => $match) {
                $input = str_replace($match, 'ᐃ' . ($i + 1) . 'ᐃ', $input);
            }
        }
        $subject = $input;
        $output = '';
        $next_line_indentation_level = 0;
        do {
            $indentation_level = $next_line_indentation_level;
            $patterns = array('/^(<([a-z]+)(?:[^>]*)>(?:[^<]*)<\\/(?:\\2)>)/' => static::MATCH_INDENT_NO, '/^<!([^>]*)>/' => static::MATCH_INDENT_NO, '/^<(input|link|meta|base|br|img|source|hr)([^>]*)>/' => static::MATCH_INDENT_NO, '/^<(animate|stop|path|circle|line|polyline|rect|use)([^>]*)\\/>/' => static::MATCH_INDENT_NO, '/^<[^\\/]([^>]*)>/' => static::MATCH_INDENT_INCREASE, '/^<\\/([^>]*)>/' => static::MATCH_INDENT_DECREASE, '/^<(.+)\\/>/' => static::MATCH_INDENT_DECREASE, '/^(\\s+)/' => static::MATCH_DISCARD, '/([^<]+)/' => static::MATCH_INDENT_NO);
            $rules = array('NO', 'DECREASE', 'INCREASE', 'DISCARD');
            foreach ($patterns as $pattern => $rule) {
                if ($match = preg_match($pattern, $subject, $matches)) {
                    $this->log[] = array('rule' => $rules[$rule], 'pattern' => $pattern, 'subject' => $subject, 'match' => $matches[0]);
                    $subject = mb_substr($subject, mb_strlen($matches[0]));
                    if ($rule === static::MATCH_DISCARD) {
                        break;
                    }
                    if ($rule === static::MATCH_INDENT_NO) {
                    } else {
                        if ($rule === static::MATCH_INDENT_DECREASE) {
                            $next_line_indentation_level--;
                            $indentation_level--;
                        } else {
                            $next_line_indentation_level++;
                        }
                    }
                    if ($indentation_level < 0) {
                        $indentation_level = 0;
                    }
                    $output .= str_repeat($this->options['indentation_character'], $indentation_level) . $matches[0] . "\n";
                    break;
                }
            }
        } while ($match);
        $interpreted_input = '';
        foreach ($this->log as $e) {
            $interpreted_input .= $e['match'];
        }
        if ($interpreted_input !== $input) {
            throw new Exception\RuntimeException('Did not reproduce the exact input.');
        }
        $output = preg_replace('/(<(\\w+)[^>]*>)\\s*(<\\/\\2>)/', '\\1\\3', $output);
        foreach ($this->temporary_replacements_script as $i => $original) {
            $output = str_replace('<script>' . ($i + 1) . '</script>', $original, $output);
        }
        foreach ($this->temporary_replacements_inline as $i => $original) {
            $output = str_replace('ᐃ' . ($i + 1) . 'ᐃ', $original, $output);
        }
        return trim($output);
    }

 public function render()
 {
     $this->addStylesheet('css/bootstrap.css');
     $output = parent::render();
     $indenter = new Indenter();
     return $indenter->indent($output);
 }