Getting the error fetching the data using http api

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PHP

HTTP

function getcartdata($acctoken)
{
	$url = "https://api.us-central1.gcp.commercetools.com/demo-commerce/carts/8d9e4d12-2a5f-4bd4-a4af-97d2bd9b320c";
	$requestmethod = "GET";
	$cartdata = getRequest($url, $requestmethod,$acctoken);
	
	return $cartdata;
}
$cartresult = getcartdata($access_token); 
 $dcart = json_decode($cartresult);  
echo $limit = count($dcart['lineItems']);

Error is Call to undefined function getRequest()
and getting the value in $access_token. The api working fine in postman

What I have tried:

Tried changing the variable sin value but still not working