How do you autopopulate a related field in custom module from a related field of another module?

$account = new Account();
$account->retrieve($bean->account_id);

$supplier = new Supplier();
$supplier->retrieve($account->supplier_id);

include_once('<your path to my function>/getRelashionshipByModules.php'); $suppliers = array();
$order_to_account_relationship = getRelationshipByModules ('Order_Management', 'Accounts');
$account_to_supplier_relationship = getRelationshipByModules('Account', 'Suppliers');
$bean->load_relationship($order_to_account_relationship);
//loop through the Accounts linked to the Order
foreach($bean->$order_to_account_relationship->getBeans() as $account){
    //loop through the suppliers for this account
    $account->load_relationship($account_to_supplier_relationship);
    foreach($account->$account_to_supplier_relationship->getBeans as $supplier){        //check for duplicated by id (the key of the array)        //if you don't already have this supplier in your list, add it.
       if(!array_key_exists($supplier->id, $suppliers)) $suppliers[ $supplier->id] = $supplier->name;
   }
}
//the array $suppliers now contains all your suppliers with key the id of the record and value the name of the supplier.

$account->retrieve($bean->account_id);

$account->field_name;

$account->field_name_c; //for a custom field

$bean->load_relationship($order_to_account_relationship);

Call to a member function load_relationship() on a non-object in /../custom/modules/Cproj_order_management01/converToInvoice.php on line 95, referer: ..=Cproj_order_management01&action=DetailView&record=420d92b1-1cde-725b-b6ef-522725fbaf91

require_once('modules/Cproj_order_management01/Cproj_order_management01.php');
require_once('modules/AOS_Invoices/AOS_Invoices.php');
require_once('modules/Accounts/Account.php');
require_once('modules/a122_Suppliers/a122_Suppliers.php');
require_once('modules/Relationships/Relationship.php');

global $timedate;
   //your function
function getRelationshipByModules ($m1, $m2)
{
global $db,$dictionary,$beanList;
$rel = new Relationship;
if($rel_info = $rel->retrieve_by_sides($m1, $m2, $db)){
$bean = BeanFactory::getBean($m1);
$rel_name = $rel_info['relationship_name'];
foreach($bean->field_defs as $field=>$def){
 if(isset($def['relationship']) && $def['relationship']==$rel_name) {
  return(array($def['name'], $m1));
 }
}
} elseif($rel_info = $rel->retrieve_by_sides($m2, $m1, $db)){
$bean = BeanFactory::getBean($m2);
$rel_name = $rel_info['relationship_name'];
foreach($bean->field_defs as $field=>$def){
 if(isset($def['relationship']) && $def['relationship']==$rel_name) {   
               return(array($def['name'], $m2));
 }
   }
}
return(FALSE);
}
$invoice=new AOS_Invoices();
//$om=new Cproj_order_management01();

$suppliers=array();

$order_to_account_relationship = getRelationshipByModules ('Cproj_order_management01', 'Accounts');
$account_to_supplier_relationship = getRelationshipByModules('Accounts', 'a122_Suppliers');
$bean->load_relationship($order_to_account_relationship);
foreach($bean->$order_to_account_relationship->getBeans() as $account){
$account->load_relationship($account_to_supplier_relationship);
foreach($account->$account_to_supplier_relationship->getBeans() as $supplier){
  
if(!array_key_exists($supplier->id, $suppliers))  
      $suppliers[ $supplier->id] = $supplier->name;
}
}
//when It works I'm gonna use that fields to fill my invoice fields
[......]

$invoice->save();

ob_clean();
header('Location: index.php?module=AOS_Invoices&action=EditView&record='.$invoice->id);

$order_to_account_relationship = getRelationshipByModules ('Cproj_order_management01', 'Accounts');
echo("relationship = " . $order_to_account_relationship);die();

//create a new bean
$invoice=new AOS_Invoices();
//for each object populate it
$invoice->field_name = "field_value";
//relate the invoice to the supplier
$invoice->supplier_id = $supplier_id //check the naming of the relate field's id
$invoice->save();