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* Newsletter form improvement * Apply suggestions from code review * Changing image and copy * Image change * Copy tweak * Tweak * Tweaks * another try * Apply suggestions from code review Co-authored-by: Lior539 <lneuner@gmail.com> * Update index.tsx * Image tweak * putting engineer post back --------- Co-authored-by: Lior539 <lneuner@gmail.com>
199 lines
7.2 KiB
Markdown
199 lines
7.2 KiB
Markdown
---
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title: How to set up feature flags in PHP
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date: 2024-02-15
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author:
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- lior-neu-ner
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tags:
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- feature flags
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---
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import { ProductScreenshot } from 'components/ProductScreenshot'
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export const EventsInPostHogLight = "https://res.cloudinary.com/dmukukwp6/image/upload/posthog.com/contents/images/tutorials/php-feature-flags/events-light.png"
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export const EventsInPostHogDark = "https://res.cloudinary.com/dmukukwp6/image/upload/posthog.com/contents/images/tutorials/php-feature-flags/events-dark.png"
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export const CreateFlagLight = "https://res.cloudinary.com/dmukukwp6/image/upload/posthog.com/contents/images/tutorials/php-feature-flags/events-light.png"
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export const CreateFlagDark = "https://res.cloudinary.com/dmukukwp6/image/upload/posthog.com/contents/images/tutorials/php-feature-flags/events-dark.png"
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export const FlagCaptureLight = "https://res.cloudinary.com/dmukukwp6/image/upload/posthog.com/contents/images/tutorials/php-feature-flags/flag-capture-light.png"
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export const FlagCaptureDark = "https://res.cloudinary.com/dmukukwp6/image/upload/posthog.com/contents/images/tutorials/php-feature-flags/flag-capture-dark.png"
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[Feature flags](/feature-flags) help you conditionally roll out and release features safely. This tutorial shows you how integrate them in PHP using PostHog.
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We'll create a basic PHP app, add PostHog, create a feature flag, and then implement the flag to control content in our app.
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## 1. Create a basic PHP app
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First, ensure [PHP](https://www.php.net/manual/en/install.php) is installed. Then, create a new folder for your project called `php-feature-flags`. In this folder, create an `index.php` file:
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```bash
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mkdir php-feature-flags
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cd ./php-feature-flags
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touch index.php
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```
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Next, add the following code to `index.php` to set up a basic page with a heading and paragraph:
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```php file=index.php
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<?php
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$paragraphText = 'Placeholder text';
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?>
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<!DOCTYPE html>
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<html>
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<body>
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<h1>PHP feature flags tutorial</h1>
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<p><?php echo $paragraphText; ?></p>
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</body>
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</html>
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```
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Run `php -S localhost:8000` and navigate to `http://localhost:8000` to see our app in action.
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## 2. Add PostHog to your app
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With our app set up, it’s time to install and set up PostHog. If you don't have a PostHog instance, you can [sign up for free](https://us.posthog.com/signup).
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To start, make sure [Composer](https://getcomposer.org/) is installed. Then run `composer require posthog/posthog-php` to install [PostHog’s PHP SDK](/docs/libraries/php).
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Then, initialize PostHog at the top of `index.php` using your project API key and instance address (you can find these in [your project settings](https://us.posthog.com/project/settings)):
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```php file=index.php
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<?php
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require_once __DIR__ . '/vendor/autoload.php';
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use PostHog\PostHog;
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PostHog::init(
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'<ph_project_api_key>',
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['host' => '<ph_client_api_host>']
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);
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// rest of your code
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```
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Lastly, we [capture](/docs/product-analytics/capture-events) a `$pageview` event using `PostHog::capture()`:
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```php file=index.php
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<?php
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require_once __DIR__ . '/vendor/autoload.php';
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use PostHog\PostHog;
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PostHog::init(
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'<ph_project_api_key>',
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['host' => '<ph_client_api_host>']
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);
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$paragraphText = 'Placeholder text';
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$distinctId = 'placeholder-user-id';
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PostHog::capture([
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'distinctId' => $distinctId,
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'event' => '$pageview'
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]);
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?>
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<!-- your existing html code -->
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```
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With this set up, restart your app and then refresh your browser a few times. You should now see the captured event in your [PostHog activity tab](https://us.posthog.com/events).
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<ProductScreenshot
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imageLight={EventsInPostHogLight}
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imageDark={EventsInPostHogDark}
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alt="Events captured in PostHog"
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classes="rounded"
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/>
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## 3. Create a feature flag in PostHog
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With PostHog set up, your app is ready for feature flags. To create one, go to the [feature flags tab](https://us.posthog.com/feature_flags) in PostHog and click **New feature flag**. Enter a flag key (like `my-cool-flag`), set the release condition to roll out to 100% of users, and press "Save."
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<ProductScreenshot
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imageLight={CreateFlagLight}
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imageDark={CreateFlagDark}
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alt="Feature flag created in PostHog"
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classes="rounded"
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/>
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You can customize your [release conditions](/docs/feature-flags/creating-feature-flags#release-conditions) with rollout percentages, and [user](/docs/product-analytics/person-properties) or [group properties](/docs/product-analytics/group-analytics) to fit your needs.
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## 4. Implement the flag code
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To implement the feature flag, we:
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1. Fetch the `my-cool-flag` flag using [`PostHog::isFeatureEnabled()`](/docs/libraries/php#feature-flags).
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2. Update the paragraph text based on whether the flag is enabled or not.
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```php file=index.php
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<?php
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require_once __DIR__ . '/vendor/autoload.php';
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use PostHog\PostHog;
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PostHog::init(
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'<ph_project_api_key>',
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['host' => '<ph_client_api_host>']
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);
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$paragraphText = 'Placeholder text';
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$distinctId = 'placeholder-user-id';
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// fetch the feature flag
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$isFlagEnabled = PostHog::isFeatureEnabled(
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'my-cool-flag',
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$distinctId
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);
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if ($isFlagEnabled) {
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$paragraphText = "Flag enabled!";
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} else {
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$paragraphText = "Flag disabled!";
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}
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// rest of your code
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```
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When you restart your app and refresh the page, you should see the text updated to `Flag enabled!`.
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> **💡 Setting the correct `distinctId`:**
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>
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> You may notice that we set `$distinctId = 'placeholder-user-id'` in our flag call above. In production apps, to ensure you fetch the correct flag value for your user, `distinctId` should be set to their unique ID.
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>
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> For logged-in users, you typically use their email or user ID as their `distinctId`. For logged-out users, assuming they made their request from a browser, you can use values from their request cookies. See an example of this in our [Nuxt feature flags tutorial](/tutorials/nuxt-feature-flags#setting-the-correct-distinctid).
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## 5. Include the flag when capturing your event
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To ensure any captured events are associated with the correct flag value, we need to [include our flag information when capturing](/docs/libraries/php#step-2-include-feature-flag-information-when-capturing-events) them. This enables us to breakdown [insights](/docs/product-analytics/insights) by feature flag value.
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To do this for our `$pageview` event, we add the [`$feature/my-cool-flag`](/docs/libraries/php#step-2-include-feature-flag-information-when-capturing-events) key to our event properties when capturing:
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```php file=index.php
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<?php
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// rest of your code
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PostHog::capture([
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'distinctId' => $distinctId,
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'event' => '$pageview',
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'properties' => [
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'$feature/my-cool-flag' => $isFlagEnabled
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]
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]);
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// rest of your code
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```
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Now when your event is captured, you should see the flag value in the event details in PostHog:
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<ProductScreenshot
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imageLight={FlagCaptureLight}
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imageDark={FlagCaptureDark}
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alt="Feature flag details in PostHog events"
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classes="rounded"
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/>
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## Further reading
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- [How to set up one-time feature flags](/tutorials/one-time-feature-flags)
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- [How to set up A/B tests in PHP](/tutorials/php-ab-tests)
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- [How to set up analytics in PHP](/tutorials/php-analytics)
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<NewsletterForm /> |