Highlight partial document with Codemirror

I’m using code mirror to display and highlight code extracts.
The following php extract is well highlighted because it has the php open tag at the beginning:

<?php
if (true) {

The following php extract is not well highlighted because it hasn’t the tag.

if (true) {

Which config would allow me this?
For now, I tried to play with the config without success:

import {basicSetup, EditorView} from "codemirror"
import {php} from "@codemirror/lang-php"
import {languages} from "@codemirror/language-data"

// The Markdown parser will dynamically load parsers
// for code blocks, using @codemirror/language-data to
// look up the appropriate dynamic import.
let view = new EditorView({
  doc: "if (true) {",
  plain: true,
  mode: {
    name: "php",
    startOpen: true
  },
  extensions: [
    basicSetup,
    php()
  ],
  parent: document.body
})

You can try it in this sandbox along with if (true) {.

Bonus: I’m using react-codemirror