<?php
 
$horario = "18:30";
$dias = "Seg a Ter";
/*criando objeto vazio*/
                $object = new stdClass();
                /*passando array para o objeto vazio*/
                $object->salas = array();
 
           //...AQUI INICIA UM foreach, sobre o foreach abaixo
 
 
                /*percorrendo o objeto vazio*/  
                foreach ($object as $key => $value) {           
                    $object_data = new stdClass();
                    $object_data->horario = $horario;//valor da hora
                    $object_data->data = $dias;//valor do dia
                    array_push($object->salas, $object_data);
                }
 
                /*codificando json*/    
                echo json_encode($object);

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