RMWebsec

Like a normal text widget this allows you to easily post text and HTML, but 
now you can execute PHP too! 
This makes merging with other themes easier.
!IMPORTANT! You must use tags for the code to be 
recognized.

PHP-Widgetify

Execute HTML, Text or PHP fast and easy with this Widgetify-widget.

Mario Peshev

DevriX

Create page templates like the ones in your theme folder but through a “DX Templates” menu in your Admin dashboard. Paste HTML, JS and PHP code which you could assign to your posts, pages or custom post types via a meta box dropdown. Create page templates and apply them to be evaluated.
Note: eval() function is used. However, it is available only for admin users to submit code and normally admin users could do a lot harm or upload external harmful plugins as well.
A complete demo is available here:
<iframe loading="lazy" class="youtube-player" width="750" height="422" src="https://www.youtube.com/embed/jtsbXfNi7ts?version=3&rel=1&showsearch=0&showinfo=1&iv_load_policy=1&fs=1&hl=en-US&autohide=2&wmode=transparent" allowfullscreen="true" style="border:0;" sandbox="allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox"></iframe>

DX Template Manager

Create page templates like the ones in your theme folder but through a "DX Templates" menu in your Admin dashboard - HTML, JS, PHP supported …

PHP-Widgetify vs DX Template Manager