PHP code highlighting not working for hugo

gistfile1.txt

```yaml
pygmentsuseclasses: false
pygmentsCodeFences: true
pygmentsCodeFencesGuessSyntax: true
markup:
  highlight:
    codeFences: true
    hl_Lines: ""
    lineNoStart: 1
    lineNos: true
    lineNumbersInTable: true
    noClasses: true
    style: monokai
    tabWidth: 4
```

PHP code is not highlighted.

```php
$hello = function () {
    echo "Hello World";
};
```

{{< highlight php >}}
$hello = function () {
    echo "Hello World";
};
{{< /highlight >}}

But if we add a <?php in front it will convert to html inside span with color. All below code works.

```
<?php
$hello = function () {
    echo "Hello World";
};
```

{{< highlight html >}}
<section id="main">
  <div>
    <h1 id="title">{{ .Title }}</h1>
    {{ range .Data.Pages }}
      {{ .Render "summary"}}
    {{ end }}
  </div>
</section>
{{< /highlight >}}

{{< highlight php >}}
<section id="main">
  <div>
    <h1 id="title"><?= $title ?></h1>
    <?php $value = "Hello World"; ?>
  </div>
</section>
{{< /highlight >}}

```html
<section id="main">
  <div>
    <h1 id="title"><?= $title ?></h1>
    <?php $value = "Hello World"; ?>
  </div>
</section>
```