Php equivalent needed for python snippet with Xpath custom extension

Question

I am stuck with porting a huge python code to php 8

It's using xpath custom functions inside.

Need help with below code explanation, and even better if someone can give a PHP equivalent.

Common initialization.

import html5lib
from html5lib import HTMLParser
from lxml import etree, html, cssselect

def _html5lib_parser() -> HTMLParser:
    return HTMLParser(
        html5lib.treebuilders.getTreeBuilder("lxml"),
        namespaceHTMLElements=False
    )


html_message=html5parser.document_fromstring(s,parser=_html5lib_parser())

Snippet 1: Xpath with user defined function

def text_content(context):
    """XPath Extension to return text content of a node"""
    return context.context_node.xpath("string()").strip()


block = html_message.xpath(
    ("//*[starts-with(mg:text_content(), 'From:')]|"
     "//*[starts-with(mg:text_content(), 'Date:')]"))
         
         
if block:
    block = block[-1]
    parent_div = None

Snippet 2: Xpath with another user defined function

def tail(context):
    """XPath Extension function to return tail text of a node"""
    return context.context_node.tail or ''

block = html_message.xpath(
        ("//*[starts-with(mg:tail(), 'From:')]|"
         "//*[starts-with(mg:tail(), 'Date:')]"))
if block:
    block = block[0]

I am using DomDocument with Xpath till now for rest of the code in Php

$html_message = new DOMDocument();
$html_message->loadHTML($html_string);

$finder = new DomXPath($html_message);
$node = $finder->query();