Automatically create a lifetime transaction for a specific product each time a user registers.

auto_enroll.php

<?php

if(is_plugin_active('memberpress/memberpress.php')) {

  add_action( 'user_register', 'mp_auto_enroll' );
  //add_action( 'gform_user_registered', 'mp_auto_enroll', 10, 4 );
  
  function mp_auto_enroll($user_id, $user_config=array(), $entry='', $user_pass='') {
    $txn = new MeprTransaction();
    $txn->user_id = $user_id;
    $txn->product_id = 8; // TODO: Make sure you change this value to whatever the product_id will be
    $txn->trans_num  = uniqid();
    $txn->status     = MeprTransaction::$complete_str;
    $txn->gateway    = MeprTransaction::$free_gateway_str;
    $txn->expires_at = 0; // 0 = Lifetime, null = product default expiration
    $txn->store();
  }

}

how to create recurring transcation with above codes pls

You'd have to create a MeprSubscription object and store it. Then assign the first Transaction to it afterwards.

$sub = new MeprSubscription();
$sub->user_id = $user_ID;
$sub->product_id = 123;
$sub->price = 12.99;
$sub->total = 12.99;
$sub->period = 1;
$sub->period_type = 'months';
$sub->status = MeprSubscription::$active_str;
$sub_id = $sub->store();

$txn = new MeprTransaction();
$txn->amount = 12.99;
$txn->total = 12.99;
$txn->user_id = $user_ID;
$txn->product_id = 123;
$txn->status = MeprTransaction::$complete_str;
$txn->txn_type = MeprTransaction::$payment_str;
$txn->gateway = 'manual';
$txn->expires_at = gmdate('Y-m-d 23:59:59', (time() + MeprUtils::months(1)));
$txn->subscription_id = $sub_id;
$txn->store();

Then every month, you'd need to programatically add a new Transaction with the same $sub_id for that user.

okay thank you , worked