Paypal is very easy to integrate and there are various official SDKs available to make it easy for the developer.<p><a href="https:&#x2F;&#x2F;github.com&#x2F;paypal?utf8=%E2%9C%93&amp;query=sdk" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;paypal?utf8=%E2%9C%93&amp;query=sdk</a><p>Alternatively you can look into stripe or another payment API.    <a href="https:&#x2F;&#x2F;stripe.com&#x2F;us&#x2F;features#built-for-developers" rel="nofollow">https:&#x2F;&#x2F;stripe.com&#x2F;us&#x2F;features#built-for-developers</a>