Check If A Number Is On WhatsApp

 $url = 'https://api.wachat.net/isonwa';

 $data = [
   'receiver' => '$receiver',
   'token' => '$token',

 ];

 $ch = curl_init();
 curl_setopt($ch, CURLOPT_HTTPHEADER,  ['Content-Type: application/x-www-form-urlencoded']);
 curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'POST');
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
 curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($data));
 curl_setopt($ch, CURLOPT_URL, $url);
 curl_setopt($ch, CURLOPT_TIMEOUT, 30);
 curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
 curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
 $response = curl_exec($ch);
 curl_close($ch);

 echo $response; // output {success:true/false, isonwa:true/false}