zackdesign

This plugin is deprecated and should not be used for new installations.
PayPal API Subscriptions was built in 2008 using the PayPal NVP (Name-Value Pair) API v52.0, which PayPal has since discontinued in favour of their REST APIs. The plugin also directly handles raw credit card numbers on your server, which creates PCI compliance obligations that most WordPress sites cannot meet.
Recommended alternatives:
<ul>
<li><a href="https://woocommerce.com/products/woocommerce-paypal-payments/" rel="nofollow ugc">WooCommerce + PayPal Payments</a> — modern PayPal integration with Smart Buttons (card data never touches your server)</li>
<li><a href="https://www.memberpress.com/" rel="nofollow ugc">MemberPress</a> — full membership/subscription management with PayPal and Stripe</li>
<li><a href="https://www.paidmembershipspro.com/" rel="nofollow ugc">Paid Memberships Pro</a> — free membership plugin with PayPal support</li>
</ul>
What happens in v1.2.0:
<ul>
<li>Existing <code>[ppsa]</code> shortcodes display a retirement message instead of subscription buttons</li>
<li>An admin notice reminds you to migrate</li>
<li>All PayPal API code, the credit card form, and bundled jQuery have been removed</li>
</ul>

PayPal API Subscriptions

DEPRECATED — This plugin uses the discontinued PayPal NVP API and handles raw credit card data. Please switch to a modern alternative.

Brian Fegter

WP_DEBUG works well, however is not inclusive of all theme/plugin files that might not be loaded during certain page loads. Deprecation Checker allows you to view all the deprecated functions complete with path, line number, deprecation function name, and the new recommended function to use.
Deprecated files are collated directly from WordPress core itself, so this plugin is scalable with future versions of WordPress.
We’ve included a couple handy filters and constants to make this plugin flexible for your own needs:
<ul>
<li>Turn off plugin/theme directory checks</li>
<li>Add your own custom paths to check</li>
<li>Add your own deprecated functions to the search</li>
</ul>

Deprecation Checker

Deprecation Checker simply scans your plugins, themes, and custom directories for deprecated functions.

PayPal API Subscriptions vs Deprecation Checker