HTML-DOM/lib/Printer.php

<?php
declare(strict_types=1);
namespace dW\HTML5;

class Printer {

    public static function serialize($node): string {
        if (!$node instanceof DOMElement && !$node instanceof DOMDocument && !$node instanceof DOMDocumentFragment) {
            throw new Exception(Exception::PRINTER_DOMELEMENT_DOMDOCUMENT_DOMDOCUMENTFRAG_EXPECTED, gettype($node));
        }

        # 1. Let s be a string, and initialize it to the empty string.
        $s = '';

        # 2. If the node is a template element, then let the node instead be the
        # template element’s template contents (a DocumentFragment node).
        // TODO

        # 3. For each child node of the node, in tree order, run the following steps:
        for ($i = 0; $i < $node->childNodes->length; $i++) {
            # 1. Let current node be the child node being processed.
            $currentNode = $node->childNodes->item($i);

            # 2. Append the appropriate string from the following list to s:
            ## If current node is an Element
            ### If current node is an element in the HTML namespace, the MathML namespace,
            ### or the SVG namespace, then let tagname be current node’s local name.
            ### Otherwise, let tagname be current node’s qualified name.
            if ($currentNode instanceof DOMElement && (is_null($currentNode->namespaceURI) || $currentNode->namespaceURI === Parser::MATHML_NAMESPACE || $currentNode->namespaceURI === Parser::SVG_NAMESPACE)) {
                $tagName = $currentNode->localName;
            } else {
                $tagName = $currentNode->nodeName;
            }

            ### Append a U+003C LESS-THAN SIGN character (<), followed by tagname.
            $s .= "<$tagName";

            ### For each attribute that the element has, append a U+0020 SPACE character,
            ### the attribute’s serialized name as described below, a U+003D EQUALS SIGN
            ### character (=), a U+0022 QUOTATION MARK character ("), the attribute’s value,
            ### escaped as described below in attribute mode, and a second U+0022 QUOTATION
            ### MARK character (").
            for ($j = 0; $j < $currentNode->attributes->length; $j++) {
                $attr = $currentNode->attributes->item($j);

                # An attribute’s serialized name for the purposes of the previous paragraph
                # must be determined as follows:
                switch ($attr->namespaceURI) {
                    # If the attribute has no namespace
                    case null:
                        # The attribute’s serialized name is the attribute’s local name.
                        $name = $attr->localName;
                    break;
                    # If the attribute is in the XML namespace
                    case Parser::XML_NAMESPACE:
                        # The attribute’s serialized name is the string "xml:" followed by the
                        # attribute’s local name.
                        $name = 'xml:' . $attr->localName;
                    break;
                    # If the attribute is in the XMLNS namespace...
                    case Parser::XMLNS_NAMESPACE:
                        # ...and the attribute’s local name is xmlns
                        if ($attr->localName === 'xmlns') {
                            # The attribute’s serialized name is the string "xmlns".
                            $name = 'xmlns';
                        }
                        # ...and the attribute’s local name is not xmlns
                        else {
                            # The attribute’s serialized name is the string "xmlns:" followed by the
                            # attribute’s local name.
                            $name = 'xmlns:' . $attr->localName;
                        }
                    break;
                    # If the attribute is in the XLink namespace
                    case Parser::XLINK_NAMESPACE:
                        # The attribute’s serialized name is the string "xlink:" followed by the
                        # attribute’s local name.
                        $name = 'xlink:' . $attr->localName;
                    break;
                    # If the attribute is in some other namespace
                    default:
                        # The attribute’s serialized name is the attribute’s qualified name.
                        $name = $attr->name;
                }

                $value = static::escapeString($attr->value, true);

                $s .= " $name=\"$value\"";
            }

            ### While the exact order of attributes is UA-defined, and may depend on factors
            ### such as the order that the attributes were given in the original markup, the
            ### sort order must be stable, such that consecutive invocations of this
            ### algorithm serialize an element’s attributes in the same order.
            // Okay.

            ### Append a U+003E GREATER-THAN SIGN character (>).
            $s .= '>';
        }
    }

    protected static escapeString(string $string, bool $attribute = false): string {
        # Escaping a string (for the purposes of the algorithm above) consists of
        # running the following steps:
        ## 1. Replace any occurrence of the "&amp;" character by the string "&amp;amp;".
        ## 2. Replace any occurrences of the U+00A0 NO-BREAK SPACE character by the
        ## string "&amp;nbsp;".
        $string = str_replace(['&amp;', chr(0x00A0)], ['&amp;amp;', '&amp;nbsp;'], $string);
        ## 3. If the algorithm was invoked in the attribute mode, replace any
        ## occurrences of the "&quot;" character by the string "&amp;quot;".
        ## 4. If the algorithm was not invoked in the attribute mode, replace any
        ## occurrences of the "&lt;" character by the string "&amp;lt;", and any
        ## occurrences of the "&gt;" character by the string "&amp;gt;".
        if ($attribute) {
            $string = str_replace(['&quot;', '&lt;', '&gt;'], ['&amp;quot;', '&amp;lt;', '&amp;gt;'], $string);
        }

        return $string;
    }
}