<?php
$_POST['ali'] = "asdasd";
$_POST['veli'] = "asdasd";
$_POST['serdar'] = "asdasd";

function post_isset() {
   $args = func_get_args();
   foreach($args as $arg) {
      if( !isset($_POST[$arg]) ) {
         return false;
      }
   }
   return true;
}

echo post_isset('asdasd') ? 'true' . "\n" : 'false' . "\n";

echo post_isset('ali', 'serdar') ? 'true' . "\n" : 'false' . "\n";

echo post_isset('ali', 'veli', 'serdar') ? 'true' . "\n" : 'false' . "\n";

echo post_isset('ali', 'veli', 'serdar', 'memo') ? 'true' . "\n" : 'false' . "\n";

?>

false
true
true
false