Use of undefined constant ‘assets - assumed '‘assets' (this will throw an Error in a future version of PHP)

What does this error mean? I’m struggling to wrap my head around it and can’t find similar situations online

I am trying to embed a widget and pull the svg from the site instance

Here is the code:
<healcode-widget data-version="0.2" data-link-class="healcode-pricing-option-image-link" data-site-id="96902" data-mb-site-id="468531" data-type="pricing-link" data-inner-html="<?= svg(‘assets/graphics/button.svg’) ?>" data-service-id="100004" />

Are these proper single quotes? At least when copied into here they look like apostrophies…