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> For other versions, use one of these documentation indexes:
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> For clean Markdown content of this page, append .md to this URL. For the complete documentation index, see https://buildwithfern.com/learn/llms.txt.

# Adding custom code

> Learn how to add custom logic, methods, and dependencies to your PHP SDK. Step-by-step guide to extending Fern-generated PHP clients.

> **You're viewing the legacy SDK docs**
>
> These pages cover SDK generation configured with `generators.yml`. New projects use `sdk-config.yml`, so see [the Current version of this page](/learn/sdks/generators/php/custom-code) for up-to-date guidance. To move an existing project, follow the [SDK Config migration guide](/learn/sdks/legacy/generators/migration-guides/sdk-config), which walks through `fern sdk migrate`, and review the [`sdk-config.yml` reference](/learn/sdks/reference/sdk-config).

> **Enterprise feature**
>
> This feature is available only for the [Enterprise plan](https://buildwithfern.com/pricing). To get started, reach out to [support@buildwithfern.com](mailto:support@buildwithfern.com).

This page covers how to add custom logic, methods, and dependencies to your PHP SDK.

## Adding custom logic

To get started adding custom code:

> **Note**
>
> These steps cover adding a new custom file to the SDK. To preserve line-level edits to a generated file, use [Replay](/learn/sdks/legacy/overview/custom-code#replay) instead.

#### Create a new file and add your custom logic

**`src/Helper.php`**

```php title="src/Helper.php"
<?php

namespace YourNamespace;

class Helper
{
    public static function myHelper(): void
    {
        echo "Hello World!";
    }
}
```

#### Add your file to \`.fernignore\`

**`.fernignore`**

```yaml {3} title=".fernignore"
# Specify files that shouldn't be modified by Fern

src/Helper.php
```

#### Consume the helper

Now your users can consume the helper function by importing it from the SDK.

```php
<?php

use YourNamespace\Helper;

Helper::myHelper();
```

## Adding custom SDK methods

Fern also allows you to add custom methods to the SDK itself (e.g.
`client.my_method()` ) by inheriting the Fern generated client and then
extending it.

#### Update \`generators.yml\` configuration

Name your Fern-generated client something like `BaseClient` to reflect that this client will be extended.

**`generators.yml`**

```yaml {4} title="generators.yml"
- name: fern-php-sdk
  version: 2.30.6
  config:
    clientName: BaseClient
```

#### Import and extend the generated client

First, import the Fern generated base client and extend it. Then, add whatever methods you want.

**`src/MyClient.php`**

```php title="src/MyClient.php"
<?php

namespace YourNamespace;

class MyClient extends BaseClient
{
    public function myHelper(): void
    {
        echo "Hello World!";
    }
}
```

#### Update \`.fernignore\`

Add the `MyClient.php` to `.fernignore`.

**`.fernignore`**

```diff title=".fernignore"
+ src/MyClient.php
```

#### Consume the method

Instead of constructing the generated client, your users will want to construct the extended client.

```php
<?php

use YourNamespace\MyClient;

$client = new MyClient();
```

Now your users can consume the helper function by importing it from the SDK.

```php
$client->myHelper();
```

## Adding custom dependencies

To add packages that your custom code requires, update your `generators.yml` using the `composerJson` configuration option.

**`generators.yml`**

```yaml {4-8} title="generators.yml"
- name: fern-php-sdk
  version: 2.30.6
  config:
    composerJson:
      require:
        guzzlehttp/guzzle: "^7.0"
      require-dev:
        phpunit/phpunit: "^10.0"
```