Not able to call post function on any of the object (Product, Collect, Metafield)

[ankesh4040]

Getting error : CurlException: Request failed with HTTP Code 400.

$metafieldv =
[
'namespace' => "custom",
'key' => "ship_time",
'value' => "API updated",
'type' => 'single_line_text_field'
]
;
$metafields = $shopify->Product('7543539269680')->Metafield->post($metafieldv);

/// Getting error...............

$collectData = [
'product_id' => '7543539269680',
'collection_id' =>'281608945712',
];

$collect = $shopify->Collect->post($collectData );

/// Getting error...............