PHP SDK reference

note

This SDK is not currently supported on Harness Self-Managed Enterprise Edition (on premises).

This topic describes how to use the Harness Feature Flags PHP SDK for your PHP application.

For getting started quickly, you can use our sample code from the PHP SDK README. You can also clone and run a sample application from the PHP SDK GitHub Repository.

Important: The PHP SDK Github repository was previously known as ff-php-server-sdk it has since been renamed to ff-php-client-sdk. This is to make it clearer that the SDK requires a client SDK key. The published package is still named ff-server-sdk this will change in a future release.

Before You Begin

Make sure you've read and understood:

• Feature Flags Overview
• Getting Started with Feature Flags
• Client-Side and Server-Side SDKs
• Communication Strategy Between SDKs and Harness Feature Flags

Version

Latest SDK version can be found on GitHub Release Page

Requirements

To use this SDK, make sure you:  

• Install PHP version 7.4 or newer
• Install Composer
• Download the SDK from our GitHub repository
• Create a PHP application, or clone our sample application.
• Create a Feature Flag on the Harness Platform. If you are following along with the SDK README sample code, make sure your flag is called harnessappdemodarkmode.
• Create an SDK key and make a copy of it

Install the SDK

Use Composer to install the SDK as a dependency in your application, for example: 

composer require harness/ff-server-sdk

 Initialize the SDK

To initialize the PHP SDK, you need to:

1. Add your Client SDK key to connect to your Harness Environment.
2. Add a Target that you want to Evaluate against a Feature Flag.
3. (Optional) Configure the SDK.
4. Complete the initialization using the Client SDK Key, Target, and any Configuration parameters you set.

Add the Client SDK Key

To connect to the correct Environment that you set up on the Harness Platform, you need to add the Client SDK Key from that Environment. 

Input the Client SDK Key into the SDK_KEY parameter, for example:

$SDK_KEY = getenv("SDK_KEY") ?: "";

Add a Target

Details

What is a Target?

Targets are used to control which users see which Variation of a Feature Flag, for example, if you want to do internal testing, you can enable the Flag for some users and not others. When creating a Target, you give it a name and a unique identifier. Often Targets are users but you can create a Target from anything that can be uniquely identified, such as an app or a machine.

For more information about Targets, go to Targeting Users With Flags.

To add a Target, build it and pass in arguments for the following:

Parameter	Description	Required?	Example
identifier	Unique ID for the Target.Read Regex requirements for Target names and identifiers below for accepted characters.	Required	"identifier" => "HT_1"
name	Name for this Target. This does not have to be unique. Note: If you don’t provide a value, the name will be the same as the identifier.Read Regex requirements for Target names and identifiers below for accepted characters.	OptionalNote: If you don't want to send a name, don't send the parameter. Sending an empty argument will cause an error.	“name" => "Harness_Target_1",
attributes	Additional data you can store for a Target, such as email addresses or location.	Optional	“attributes" =>    [“email” => “sample@sample.com”]

 

Regex requirements for Target names and identifiers

Identifier

Regex: ^[A-Za-z0-9.@_-]*$
Must consist of only alphabetical characters, numbers, and the following symbols:
. (period)
@ (at sign)
-(dash)
_ (underscore)

The characters can be lowercase or uppercase but cannot include accented letters, for example Cafe_789.

Name Regex: ^[\\p{L}\\d .@_-]*$

Must consist of only alphabetical characters, numbers, and the following symbols:
. (period)
@ (at sign)
-(dash)
_ (underscore)
(space)

The characters can be lowercase or uppercase and can include accented letters, for example Café_123.

Configure the SDK

When initializing the SDK, you also have the option of providing alternative configuration by passing in the configuration options to the cfClient. 

You can configure the following base features of the SDK:

Name	Description	Default Value
base_url	The URL used to fetch Feature Flag Evaluations. When using the Relay Proxy, change this to: http://localhost:7000	No default, provide your own value.
events_url	The URL for posting metrics data to the Feature Flag service. When using the Relay Proxy, change this to: http://localhost:7000	No default, provide your own value.
expireAfter	The amount of time in seconds that data is removed from the cache.	60 (seconds)
metricsEnabled	Set to true to enable analytics.Set to false to disable analytics.Note: When enabled, analytics data is posted every 60 seconds.	true

 

For example:

$cfClient = new Client($SDK_KEY, new Target(["name" => "harness", "identifier" => "harness"]), [  
    "base_url" => "http://ff-proxy:7000",  
    "events_url" => "http://ff-proxy:7000",  
    “metricsEnabled” => “false”,
]); 

Complete the Initialization

To complete the initialization, create an instance of the Client and pass in the SDK_Key and Target, for example: 

$client = new Client($SDK_KEY, new Target(["name" => "harness", "identifier" => "harness"]));

Sample of Initializing the SDK

$SDK_KEY = getenv("SDK_KEY") ?: "";  // you can put your SDK key inside the env variable, or you can provide in the code  
$FLAG_NAME = "harnessappdemodarkmode";  
$client = new Client($SDK_KEY, new Target(["name" => "harness", "identifier" => "harness"]));

Evaluate a Flag

Evaluating a Flag is when the SDK processes all Flag rules and returns the correct Variation of that Flag for the Target you provide. 

If a matching Flag can’t be found, or the SDK can’t remotely fetch flags, the default value is returned. 

There are different methods for the different Variation types and for each method you need to pass in:

• Identifier of the Flag you want to evaluate
• The default Variation

For example:

$result = $client->evaluate($FLAG_NAME, false);

Test Your App is Connected to Harness

When you receive a response showing the current status of your Feature Flag, go to the Harness Platform and toggle the Flag on and off. Then, check your app to verify if the Flag Variation displayed is updated with the Variation you toggled.

note

The SDK must run for at least 60 seconds before it sends metrics. Please ensure metrics have not been disabled in the SDK.

Close the SDK client

In most applications, you won't need to close the SDK client.

However, you should close the SDK client if:

• Your application is about to terminate. Closing the client ensures that all associated resources are released.
• You have determined that you do not need to evaluate flags again in your application lifecycle.

important

The SDK does not evaluate flags after the client is closed.

Sample Code for a PHP Application

Here is a sample code for integrating with the PHP SDK: 

<?php   
  
require_once realpath("vendor/autoload.php");   
  
use Harness\Client;  
use OpenAPI\Client\Model\Target;  
  
$SDK_KEY = getenv("SDK_KEY") ?: "";  // you can put your key in env variable or you can provide in the code  
$FLAG_NAME = "harnessappdemodarkmode";  
  
$client = new Client($SDK_KEY, new Target(["name" => "Harness_Target_1", "identifier" => "HT_1"]));  
$result = $client->evaluate($FLAG_NAME, false);  
  
echo "Evaluation value for flag '".$FLAG_NAME."' with target 'harness': ".json_encode($result);