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<?php
class AMP_DOM_Utils {
public static function get_dom_from_content( $content ) {
$libxml_previous_state = libxml_use_internal_errors( true );
$dom = new DOMDocument;
// Wrap in dummy tags, since XML needs one parent node.
// It also makes it easier to loop through nodes.
// We can later use this to extract our nodes.
// Add utf-8 charset so loadHTML does not have problems parsing it. See: http://php.net/manual/en/domdocument.loadhtml.php#78243
$result = $dom->loadHTML( '<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body>' . $content . '</body></html>' );
libxml_clear_errors();
libxml_use_internal_errors( $libxml_previous_state );
if ( ! $result ) {
return false;
}
return $dom;
}
public static function get_content_from_dom( $dom ) {
// Only want children of the body tag, since we have a subset of HTML.
$out = '';
$body = $dom->getElementsByTagName( 'body' )->item( 0 );
// AMP elements always need closing tags.
// To force them, we can't use saveHTML (node support is 5.3+) and LIBXML_NOEMPTYTAG results in issues with self-closing tags like `br` and `hr`.
// So, we're manually forcing closing tags.
self::recursive_force_closing_tags( $dom, $body );
foreach ( $body->childNodes as $node ) {
$out .= $dom->saveXML( $node );
}
return $out;
}
public static function create_node( $dom, $tag, $attributes ) {
$node = $dom->createElement( $tag );
self::add_attributes_to_node( $node, $attributes );
return $node;
}
public static function get_node_attributes_as_assoc_array( $node ) {
$attributes = array();
if ( ! $node->hasAttributes() ) {
return $attributes;
}
foreach ( $node->attributes as $attribute ) {
$attributes[ $attribute->nodeName ] = $attribute->nodeValue;
}
return $attributes;
}
public static function add_attributes_to_node( $node, $attributes ) {
foreach ( $attributes as $name => $value ) {
$node->setAttribute( $name, $value );
}
}
public static function is_node_empty( $node ) {
return false === $node->hasChildNodes()
&& empty( $node->textContent );
}
public static function recursive_force_closing_tags( $dom, $node ) {
if ( XML_ELEMENT_NODE !== $node->nodeType ) {
return;
}
if ( self::is_self_closing_tag( $node->nodeName ) ) {
return;
}
if ( self::is_node_empty( $node ) ) {
$text_node = $dom->createTextNode( '' );
$node->appendChild( $text_node );
return;
}
$num_children = $node->childNodes->length;
for ( $i = $num_children - 1; $i >= 0; $i-- ) {
$child = $node->childNodes->item( $i );
self::recursive_force_closing_tags( $dom, $child );
}
}
private static function is_self_closing_tag( $tag ) {
// This function is called a lot; the static var prevents having to re-create the array every time.
static $self_closing_tags;
if ( ! isset( $self_closing_tags ) ) {
// https://www.w3.org/TR/html5/syntax.html#serializing-html-fragments
// Not all are valid AMP, but we include them for completeness.
$self_closing_tags = array(
'area',
'base',
'basefont',
'bgsound',
'br',
'col',
'embed',
'frame',
'hr',
'img',
'input',
'keygen',
'link',
'meta',
'param',
'source',
'track',
'wbr',
);
}
return in_array( $tag, $self_closing_tags, true );
}
}
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