您好我有一个用PHP编写的程序。我想选择一个类别并显示相关的文章。我选择了一个类别，但没有显示出一个关键词。有人帮帮我吗？
catalogo.php
<div class="col-md-4-fluid">
<form class="navbar-form navbar-left" role="search" action="buscartipo.php" method="post" enctype="multipart/form-data" class="pull-right">
<div class="input-group">
<select class="form-control" name="tipo">
<option value="" selected="selected">Buscar por tipo</option>
<option value="tecnologia">Llave T</option>
<option value="deportes">Herramientas especiales</option>
<option value="arte">Kit de puesta a punto</option>
<option value="viajes">Otros</option>
</select>
<span class="input-group-btn">
<button type="submit" class="btn btn-default"><span class="glyphicon glyphicon-search" aria-hidden="true"></span></button>
</span>
</div>
</form>
</div>
</div>
<!--Fin row buscadores-->
<!--Comienzo row ofertas-->
<div class="row" id="catalogo">
<?php
include "conexionnew.php";
if(isset($_SESSION['empleado'])){
$idempleado=$_SESSION['empleado']['id_usuario'];
$resultado=mysqli_query($conexion,"SELECT * FROM empleado where id_usuario!='$id_usuario'");
while($array=mysqli_fetch_array($resultado)){
?>
<div class="col-md-3">
<div class="thumbnail">
<a class="example-image-link" href='<?php echo($array['imagen']);?>' data-lightbox="example-set" data-title="Optional caption."><img class="example-image" src='<?php echo ($array['imagen']);?>' alt=""/></a>
<div class="caption">
<p><?php echo $array['descripcion'];?></p>
<h3><?php echo "$".$array['precio'];?></h3>
<?php echo "<p><a href='descripcion.php?id_plantilla=$array[id_plantilla]' class='btn btn-primary' role='button'>Comprar ahora</a></p>";?>
</div>
</div>
</div>
<?php
}
}else{
$resultado=mysqli_query($conexion,"SELECT * FROM articulo");
while($array=mysqli_fetch_array($resultado)){
?>
<div class="col-md-3">
<div class="thumbnail">
<a class="example-image-link" href='<?php echo($array['imagen']);?>' data-lightbox="example-set" data-title="Optional caption."><img class="example-image" src='<?php echo ($array['imagen']);?>' alt=""/></a>
<div class="caption">
<p><?php echo $array['codarticulo'];?></p>
<h3><?php echo "$".$array['precio'];?></h3>
<?php echo "<p><a href='descripcion.php?idarticulo=$array[idarticulo]' class='btn btn-primary' role='button'>Ver detalle</a></p>";?>
</div>
</div>
</div>
<?php
}
}
?>
<!--Fin row ofertas-->
</div>
</div>
值由buscartipo.php
接收<?php
session_start();
$tipo=$_POST['tipo'];
if(empty($tipo)){
echo "<script>alert('Seleccione un tipo de plantilla')</script>";
echo "<script>location.href='catalogo.php'</script>";
}
?>
<!DOCTYPE html>
<html lang="es">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="description" content="">
<meta name="author" content="">
<title>Inicio | F y F herramientas</title>
<!-- core CSS -->
<link href="css/bootstrap.min.css" rel="stylesheet">
<link href="css/font-awesome.min.css" rel="stylesheet">
<link href="css/animate.min.css" rel="stylesheet">
<link href="css/prettyPhoto.css" rel="stylesheet">
<link href="css/main.css" rel="stylesheet">
<link href="css/responsive.css" rel="stylesheet">
<script src="js/jquery.js"></script>
<script src="js/bootstrap.min.js"></script>
<script src="js/jquery.prettyPhoto.js"></script>
<script src="js/jquery.isotope.min.js"></script>
<script src="js/main.js"></script>
<script src="js/wow.min.js"></script>
<!-- para sweet alert2 -->
<script src="bower_components/es6-promise/es6-promise.auto.min.js"></script> <!-- for IE support -->
<script type="text/javascript" src="js/sweetalert2/dist/sweetalert2.min.js"></script>
<link rel="stylesheet" type="text/css" href="js/sweetalert2/dist/sweetalert2.min.css">
</head>
<body class="homepage">
<?php require_once('cabecera.php'); ?>
<section id="feature">
<div class="container">
<!--Container cabecera-->
<div class="container" id="contenido-cabecera">
<div id="titulo-cabecera">Articulos</div>
<p>Filtrado por tipo</p>
</div>
<!--Fin Container cabecera-->
<!--Comienzo container buscar por tipo-->
<div class="row" id="buscar-tipo">
<?php
include "conexionnew.php";
/*$id_articulo=$_SESSION['articulo']['idarticulo']; */
$resultado=mysqli_query($conexion,"SELECT * FROM articulo where tipo='$tipo'");
while($array=mysqli_fetch_array($resultado)){
if($array['idarticulo']!=$id_articulo){
?>
<div class="col-sm-6 col-md-3">
<div class="thumbnail">
<a class="example-image-link" href='<?php echo($array['imagen']);?>' data-lightbox="example-set" data-title="Optional caption."><img class="example-image" src='<?php echo($array['imagen']);?>' alt=""/></a>
<div class="caption">
<p><?php echo $array['descripcion'];?></p>
<h3><?php echo "$".$array['precio'];?></h3>
<?php echo "<p><a href='descripcion.php?id_plantilla=$array[id_plantilla]' class='btn btn-primary' role='button'>Comprar ahora</a> </p>";?>
</div>
</div>
</div>
<?php
}
}
?>
</div>
</div>
<!--Fin container buscar por tipo-->
</section>
<?php require_once('pie.php'); ?>
</html>