composer require amplitude/experiment-php-server

<?php
// (1) Initialize the experiment client
$experiment = new \AmplitudeExperiment\Experiment();
$client = $experiment->initializeRemote('<DEPLOYMENT_KEY>')

// (2) Fetch variants for a user
$user = \AmplitudeExperiment\User::builder()
    ->deviceId('abcdefg')
    ->userId('[email protected]')
    ->userProperties(['premium' => True])
    ->build();

$variants = $client->fetch($user)->wait();

// (3) Access a flag's variant
$variant = $variants['FLAG_KEY'] ?? null;
if ($variant) {
    if ($variant->value == 'on') {
        // Flag is on
    } else {
        // Flag is off
    }
}

<?php
// (1) Initialize the experiment client
$experiment = new \AmplitudeExperiment\Experiment();
$client = $experiment->initializeLocal('<DEPLOYMENT_KEY>');

// (2) Start the local evaluation client.
$client->start()->wait();

// (3) Evaluate a user.
$user = \AmplitudeExperiment\User::builder()
    ->deviceId('abcdefg')
    ->userId('[email protected]')
    ->userProperties(['premium' => true]) 
    ->build();

// Evaluate all flag variants
$allVariants = $client->evaluate($user);

// Evaluate a specific subset of flag variants
$specificVariants = $client->evaluate($user, [
  'my-local-flag-1',
  'my-local-flag-2',
]);

// (4) Access a flag's variant
$variant = $allVariants['FLAG_KEY'] ?? null;
if ($variant) {
    if ($variant->value == 'on') {
        // Flag is on
    } else {
        // Flag is off
    }
}