Add note about local dev and testing to all PHP docs

Author: stayallive

docs/platforms/php/guides/symfony/index.mdx

@@ -92,3 +92,13 @@ class SentryTestController extends AbstractController
 ```
 
 After you visit the `/_sentry-test` page, you can view and resolve the recorded error by logging into [sentry.io](https://sentry.io) and opening your project. Clicking on the error's title will open a page where you can see detailed information and mark it as resolved.
+
+## Local Development and Testing
+
+When Sentry is installed in your application, it will also be active when you are developing or running tests. Because PHP is single-threaded, Sentry will send events synchronously, which can slow down your application or test suite.
+
+You most likely don't want errors to be sent to Sentry when you are developing or running tests so they don't use up [quota](/pricing/quotas/). To avoid this, set the DSN value to `null` to disable sending errors to Sentry.
+
+You can also do this by not defining `SENTRY_DSN` in your `.env` or by defining it as `SENTRY_DSN=null`.
+
+If you want to use Sentry in your local development environment, you can use [Spotlight](https://spotlightjs.com/) which runs locally on your machine.

docs/platforms/php/index.mdx

@@ -80,3 +80,11 @@ try {
 If you're using Laravel's Forge platform to provision and deploy your PHP application, you can create a Sentry organization through [Forge](https://forge.laravel.com/docs/integrations/sentry.html).
 
 ![Sentry and Forge](./img/forge-sentry.png)
+
+## Local Development and Testing
+
+When Sentry is installed in your application, it will also be active when you are developing or running tests. Because PHP is single-threaded, Sentry will send events synchronously, which can slow down your application or test suite.
+
+You most likely don't want errors to be sent to Sentry when you are developing or running tests so they don't use up [quota](/pricing/quotas/). To avoid this, set the DSN value to `null` to disable sending errors to Sentry.
+
+If you want to use Sentry in your local development environment, you can use [Spotlight](https://spotlightjs.com/) which runs locally on your machine.