I saw you put in tags jQuery, then you can use it, so you will not have problems, a simple use example is.
// PHP
$retorno = array();
$sql = $pdo->prepare("SELECT * FROM users WHERE id = ?");
$sql->execute(array($_POST['id'])); 
$retorno['dados'] = $sql->fetchAll();
die(json_encode($retorno))
With this, your PHP will already return one json for your ajax that will stay that way...
function listarUsuarios(){
   $.ajax({
      type: 'POST',
      url: 'SUA URL DO ARQUIVO PHP',
      dataType: 'json',
      data: {
         id: 1
      },
      success: function(data){
          console.log(data)
          $('body').append('<h1>'data.nome'</h1>')
      }
   })
}
// Aqui você executa sua função
listarUsuarios()
And that way you solve your problem.
							
							
						 
Please explain your solution better.
– RFL