diff --git a/src/wp-includes/html-api/class-wp-html-processor.php b/src/wp-includes/html-api/class-wp-html-processor.php
index cfcd6bdb94e94..39196499fa5af 100644
--- a/src/wp-includes/html-api/class-wp-html-processor.php
+++ b/src/wp-includes/html-api/class-wp-html-processor.php
@@ -424,6 +424,120 @@ function ( WP_HTML_Token $token ): void {
};
}
+ /**
+ * Creates a fragment processor at the current node.
+ *
+ * HTML Fragment parsing always happens with a context node. HTML Fragment Processors can be
+ * instantiated with a `BODY` context node via `WP_HTML_Processor::create_fragment( $html )`.
+ *
+ * The context node may impact how a fragment of HTML is parsed. For example, consider the HTML
+ * fragment `
Inside TD?`.
+ *
+ * A BODY context node will produce the following tree:
+ *
+ * └─#text Inside TD?
+ *
+ * Notice that the `
` tags are completely ignored.
+ *
+ * Compare that with an SVG context node that produces the following tree:
+ *
+ * ├─svg:td
+ * └─#text Inside TD?
+ *
+ * Here, a `td` node in the `svg` namespace is created, and its self-closing flag is respected.
+ * This is a peculiarity of parsing HTML in foreign content like SVG.
+ *
+ * Finally, consider the tree produced with a TABLE context node:
+ *
+ * └─TBODY
+ * └─TR
+ * └─TD
+ * └─#text Inside TD?
+ *
+ * These examples demonstrate how important the context node may be when processing an HTML
+ * fragment. Special care must be taken when processing fragments that are expected to appear
+ * in specific contexts. SVG and TABLE are good examples, but there are others.
+ *
+ * @see https://html.spec.whatwg.org/multipage/parsing.html#html-fragment-parsing-algorithm
+ *
+ * @param string $html Input HTML fragment to process.
+ * @return static|null The created processor if successful, otherwise null.
+ */
+ public function create_fragment_at_current_node( string $html ) {
+ if ( $this->get_token_type() !== '#tag' ) {
+ return null;
+ }
+
+ $namespace = $this->current_element->token->namespace;
+
+ /*
+ * Prevent creating fragments at nodes that require a special tokenizer state.
+ * This is unsupported by the HTML Processor.
+ */
+ if (
+ 'html' === $namespace &&
+ in_array( $this->current_element->token->node_name, array( 'IFRAME', 'NOEMBED', 'NOFRAMES', 'SCRIPT', 'STYLE', 'TEXTAREA', 'TITLE', 'XMP', 'PLAINTEXT' ), true )
+ ) {
+ return null;
+ }
+
+ $fragment_processor = static::create_fragment( $html );
+ if ( null === $fragment_processor ) {
+ return null;
+ }
+
+ $fragment_processor->compat_mode = $this->compat_mode;
+
+ $fragment_processor->context_node = clone $this->state->current_token;
+ $fragment_processor->context_node->bookmark_name = 'context-node';
+ $fragment_processor->context_node->on_destroy = null;
+
+ $fragment_processor->state->context_node = array( $fragment_processor->context_node->node_name, array() );
+
+ $attribute_names = $this->get_attribute_names_with_prefix( '' );
+ if ( null !== $attribute_names ) {
+ foreach ( $attribute_names as $name ) {
+ $fragment_processor->state->context_node[1][ $name ] = $this->get_attribute( $name );
+ }
+ }
+
+ $fragment_processor->breadcrumbs = array( 'HTML', $fragment_processor->context_node->node_name );
+
+ if ( 'TEMPLATE' === $fragment_processor->context_node->node_name ) {
+ $fragment_processor->state->stack_of_template_insertion_modes[] = WP_HTML_Processor_State::INSERTION_MODE_IN_TEMPLATE;
+ }
+
+ $fragment_processor->reset_insertion_mode_appropriately();
+
+ /*
+ * > Set the parser's form element pointer to the nearest node to the context element that
+ * > is a form element (going straight up the ancestor chain, and including the element
+ * > itself, if it is a form element), if any. (If there is no such form element, the
+ * > form element pointer keeps its initial value, null.)
+ */
+ foreach ( $this->state->stack_of_open_elements->walk_up() as $element ) {
+ if ( 'FORM' === $element->node_name && 'html' === $element->namespace ) {
+ $fragment_processor->state->form_element = clone $element;
+ $fragment_processor->state->form_element->bookmark_name = null;
+ $fragment_processor->state->form_element->on_destroy = null;
+ break;
+ }
+ }
+
+ $fragment_processor->state->encoding_confidence = 'irrelevant';
+
+ /*
+ * Update the parsing namespace near the end of the process.
+ * This is important so that any push/pop from the stack of open
+ * elements does not change the parsing namespace.
+ */
+ $fragment_processor->change_parsing_namespace(
+ $this->current_element->token->integration_node_type ? 'html' : $namespace
+ );
+
+ return $fragment_processor;
+ }
+
/**
* Stops the parser and terminates its execution when encountering unsupported markup.
*
diff --git a/tests/phpunit/tests/html-api/wpHtmlProcessor.php b/tests/phpunit/tests/html-api/wpHtmlProcessor.php
index 1ca60e691f03e..a19af13c78925 100644
--- a/tests/phpunit/tests/html-api/wpHtmlProcessor.php
+++ b/tests/phpunit/tests/html-api/wpHtmlProcessor.php
@@ -1043,6 +1043,66 @@ public function test_ensure_next_token_method_extensibility( $html, $expected_to
$this->assertEquals( $expected_token_counts, $processor->token_seen_count, 'Snapshot: ' . var_export( $processor->token_seen_count, true ) );
}
+ /**
+ * @ticket 62357
+ */
+ public function test_create_fragment_at_current_node_in_foreign_content() {
+ $processor = WP_HTML_Processor::create_full_parser( '