I wrote the following code in php, I would like it to show the items in an ordered way according to the combobox of the form, but in it it only orders items from the first page. Thanks!
<html lang="pt-br">
<head>
<title>Livros</title>
<meta charset="utf-8">
<link rel="stylesheet" type="text/css" href="_css/style.css">
</head>
<body>
<header>
<form method="get">
<select name="ordem">
<option>Selecione</option>
<option value="ano_public">Ano</option>
<option value="autor">Autor</option>
<option value="codigo">Codigo</option>
<option value="titulo">Titulo</option>
</select>
<input type="text" name="filtro">
<input type="submit" name="Enviar">
</form>
</header>
<?php
@$filtro = isset($_GET["filtro"]) ? $_GET["filtro"] : "codigo";
$ordem = isset($_GET["ordem"]) ? $_GET["ordem"] : "codigo";
$link = mysqli_connect("127.0.0.1","root","","db_aula");
$sql = "SELECT COUNT(*) qtde FROM tb_livro";
$rs = mysqli_query($link, $sql);
$r = mysqli_fetch_array($rs);
$total = $r['qtde'];
$qtde = 4;
$num_pags = ceil($total/$qtde);
$pagina = empty($_GET['pagina']) ? 1 : $_GET['pagina'];
$sql = "SELECT codigo, titulo, autor, ano_public FROM tb_livro ORDER BY $ordem LIMIT ".($pagina-1)*$qtde.", $qtde";
$rs = mysqli_query($link, $sql);
while($r = mysqli_fetch_array($rs)){
$r = array_map('utf8_encode', $r);
$foto = "_img/". $r["codigo"].".jpg";
if(!file_exists($foto)) $foto = "./fotos/nophoto.jpg";
echo '<div class="livro">' .
'<img src="'.$foto.'" class="foto">' .
'<span class="info">Codigo: '.$r["codigo"] .
'</span><br><br>Titulo: ' . $r["titulo"] .
'<br />Autor: ' . $r["autor"] .
'<br />Ano de publicação: ' . $r["ano_public"] . '<br/>' .
'</div>';
}
echo "<ul align='center'>";
for($i=1; $i<=$num_pags; $i++) {
if($i!=$pagina)
echo "<li><a href=\"?pagina=$i\">$i</a></li>";
else
echo "<li>$i</li>";
}
echo "</ul>";
mysqli_free_result($rs);
mysqli_close($link);
?>
</body>
</html>