PHP asynchronous Http call using curl,shell_exec

?>php

for ($i = 0; $i < 100; $i++){

  $cmd = 'nohup curl -H "Authorization: Basic yourRandomIOhere==" -H "Content-Type:        application/json" -X POST -d "{yourjson: "value"}" https://example.com/Message/ > status.out &';

  shell_exec($cmd);

}

print 'job done!';

?>

here:
100 : No of times you want to make this call
nohup:  to run in background
POST: http method, POST or GET
Authorization and content type is your option.