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

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

{
	"data": {
		"stjCd": "GJ019",
		"lgnm": "ANANT FRAGRANCE PRIVATE LIMITED",
		"stj": "Ghatak 19 (Ahmedabad)",
		"dty": "Regular",
		"adadr": [],
		"cxdt": "",
		"nba": [
			"Retail Business",
			"Warehouse / Depot",
			"Factory / Manufacturing",
			"Office / Sale Office",
			"Wholesale Business"
		],
		"gstin": "24AAACA9580A1Z1",
		"lstupdt": "16/01/2023",
		"rgdt": "01/07/2017",
		"ctb": "Private Limited Company",
		"pradr": {
			"addr": {
				"bnm": "CHANDULAL ESTATE , NR.KEVAL KANTA",
				"st": "NAGARWEL HANUMAN ROAD , RAKHIAL",
				"loc": "AHMEDABAD",
				"bno": "4 - 6",
				"stcd": "Gujarat",
				"dst": "Ahmedabad",
				"city": "",
				"flno": "GROUND FLOOR",
				"lt": "",
				"pncd": "380023",
				"lg": ""
			},
			"tradeNam": "ANANT FRAGRANCE PRIVATE LIMITED",
			"sts": "Active",
			"ctjCd": "WS0102",
			"ctj": "RANGE II",
			"einvoiceStatus": "Yes"
		}
	}
}