$curl = curl_init();
curl_setopt_array($curl, [
	CURLOPT_URL => "https://www.falconebiz.com/api/get_gstin",
	CURLOPT_RETURNTRANSFER => true,
	CURLOPT_TIMEOUT => 30,
	CURLOPT_CUSTOMREQUEST => "GET",
	CURLOPT_HTTPHEADER => [
		"Content-Type: application/json",
		"Authorization: YOUR-API-KEY",
		"Name: LEGAL_NAME OR PAN",
		"Domain: YOUR DOMAIN"
	],
]);

$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);
if($err) {
	echo "cURL Error #:" . $err;
}else{
	echo $response;
}

{"data":[
	{
		"lgnm":"ARINE SOLUTIONS PRIVATE LIMITED",
		"gstin":"27AASCA8698P1Z9"
	},
	{
		"company_name":"DRISHTI MARINE SOLUTIONS PRIVATE LIMITED",
		"gstin":"27AAACL6405F1ZS"
	},
	{
		"lgnm":"HY-POWER MARINE SOLUTIONS PRIVATE LIMITED",
		"gstin":"33AABCH8002M1ZQ"
	}
]}