Please refer faq: Q) How to load grid based on $_POST data from other page.

Yes I use GET from other page

<?php
include ("../conectar.php");
$codalbarantmp=$_POST["codalbarantmp"];
$modif=$_POST["modif"];
$tipuscaja=$_POST["tipuscaja"];
$retorno=0;
if ($modif<>1) {
if (!isset($codalbarantmp)) {
$codalbarantmp=$_GET["codalbarantmp"];
$retorno=1; }
if ($retorno==0 && $tipuscaja==1) {
$codfamilia=$_POST["codfamilia"];
$codarticulo=$_POST["codarticulo"];
$cajas=$_POST["cajas"];
$unidadescajas=$_POST["unidadescajas"];
$cantidad=$_POST["cantidad"];
$precio=$_POST["precio"];
$importe=$_POST["importe"];
$descuento=$_POST["descuento"];
$codubicacion=$_POST["codubicacion"];
$sel_insert="INSERT INTO pedidoslineatmp (codalbaran,numlinea,codigo,codfamilia,cajas,unidades_caja,cantidad,precio,importe,dcto,inv) VALUES ('$codalbarantmp','','$codarticulo','$codfamilia','$cajas','$unidadescajas','$cantidad','$precio','$importe','$descuento','$codubicacion')";
$rs_insert=mysql_query($sel_insert);

$query_tmp="SELECT * FROM cajlinea WHERE codcaja='$codarticulo' ORDER BY numlinea ASC";
$rs_tmp=mysql_query($query_tmp);
$contador=0;

while ($contador < mysql_num_rows($rs_tmp)) {
$codarticulo_caja=mysql_result($rs_tmp,$contador,"codigo");
$unidadescajas=mysql_result($rs_tmp,$contador,"unidades_caja");
$descuento1= ($descuento/100);
$cantidad=($cajas * $unidadescajas);
$importe= ($cantidad * $precio);
$importe=($importe-($importe * $descuento1));

$sel_insert="INSERT INTO pedidoslineatmp (codalbaran,numlinea,codigo,codfamilia,cajas,unidades_caja,cantidad,precio,importe,dcto,inv) VALUES ('$codalbarantmp','','$codarticulo_caja','$codfamilia','$cajas','$unidadescajas','$cantidad','$precio','$importe','$descuento','$codubicacion')";
$rs_insert=mysql_query($sel_insert);

$contador++;
}
}
}

/**
* PHP Grid Component
*
* @author Abu Ghufran <[email protected]> – http://www.phpgrid.org
*/

$conn = mysql_connect("localhost", "root", "***");
mysql_select_db("****");

mysql_query("SET NAMES 'utf8'");

include("../grid/inc/jqgrid_dist.php");

$col = array();
$col["title"] = "Id"; // caption of column
$col["name"] = "codalbaran, numlinea"; // grid column name, must be exactly same as returned column-name from sql (tablefield or field-alias)
$col["width"] = "10";
$col["hidden"] = true;
$cols[] = $col;

$col = array();
$col["title"] = "Codalba"; // caption of column
$col["name"] = "codalbaran"; // grid column name, must be exactly same as returned column-name from sql (tablefield or field-alias)
$col["width"] = "10";
//$col["hidden"] = true;
$cols[] = $col;

$cols[] = $col;
$g = new jqgrid();
// $grid["url"] = ""; // your paramterized URL — defaults to REQUEST_URI
$grid["rowNum"] = 10; // by default 20
$grid["sortname"] = 'codalbaran'; // by default sort grid by this field
$grid["sortorder"] = "desc"; // ASC or DESC
$grid["caption"] = "$codalbarantmp"; // caption of grid
$grid["autowidth"] = true; // expand grid to screen width
$grid["multiselect"] = true; // allow you to multi-select through checkboxes

$g->set_options($grid);

$g->set_actions(array(
"add"=>true, // allow/disallow add
"edit"=>true, // allow/disallow edit
"delete"=>true, // allow/disallow delete
"rowactions"=>true, // show/hide row wise edit/del/save option
"search" => "advance" // show single/multi field search condition (e.g. simple or advance)
)
);

// you can provide custom SQL query to display data
//$g->select_command = "SELECT * FROM (SELECT i.codalbaran, i.numlinea, c.referencia, c.descripcion, i.cantidad, i.importe FROM pedidoslineatmp i INNER JOIN articulos c ON i.codigo = c.codarticulo WHERE i.codalbaran='$codalbarantmp') o";

$g->select_command = "SELECT * FROM (SELECT i.codalbaran, i.numlinea, c.referencia, c.descripcion, i.cantidad, i.importe FROM pedidoslineatmp i INNER JOIN articulos c ON i.codigo = c.codarticulo WHERE i.codalbaran = '$codalbarantmp') o";

$g->table = "pedidoslineatmp";

// pass the cooked columns to grid
$g->set_columns($cols);

// generate grid output, with unique grid name as 'list1'
$out = $g->render("list1");

I've used the sentence

if (!empty($_POST["codalbarantmp"]))
{
$_SESSION["codalbarantmp"] = $_POST["codalbarantmp"];
}
$pid = $_SESSION["codalbarantmp"];

$grid["caption"] = "$pid"; // caption of grid… I can see VARIABLE but the sentence in custom Sql dont show nothing

$g->select_command = "SELECT * FROM (SELECT i.codalbaran, i.numlinea, c.referencia, c.descripcion, i.cantidad, i.importe FROM pedidoslineatmp i INNER JOIN articulos c ON i.codigo = c.codarticulo WHERE i.codalbaran = '$pid') o";

Please make sure you are usng session_start(); call before using $_SESSION vars.

Yes, I don't add

session_start();
Now works perfect thanks for all.