Here is the master PHP code,

<?php
include_once ("conexion.php");

// to the url parameter are added 4 parameters as described in colModel
// we should get these parameters to construct the needed query
// Since we specify in the options of the grid that we will use a GET method
// we should use the appropriate command to obtain the parameters.
// In our case this is $_GET. If we specify that we want to use post
// we should use $_POST. Maybe the better way is to use $_REQUEST, which
// contain both the GET and POST variables. For more information refer to php documentation.
// Get the requested page. By default grid sets this to 1.
include("php/JSON.php");

$json = new Services_JSON();

$page = $_GET['page'];

// get how many rows we want to have into the grid - rowNum parameter in the grid
$limit = $_GET['rows'];

// get index row - i.e. user click to sort. At first time sortname parameter -
// after that the index from colModel
$sidx = $_GET['sidx'];

// sorting order - at first time sortorder
$sord = $_GET['sord'];

// if we not pass at first time index use the first column for the index or what you want
if(!$sidx) $sidx =1;

// connect to the MySQL database server and the database, too
$Conexion=new Conexion();
$Conexion->getConexion();

// calculate the number of rows for the query. We need this to paging the result
$result = mysql_query("SELECT COUNT(*) AS count FROM requisicion_p");
$row = mysql_fetch_array($result,MYSQL_ASSOC);
$count = $row['count'];

// calculate the total pages for the query
if( $count > 0 && $limit > 0) {
$total_pages = ceil($count/$limit);
} else {
$total_pages = 0;
}

// if for some reasons the requested page is greater than the total
// set the requested page to total page
if ($page > $total_pages) $page=$total_pages;

// calculate the starting position of the rows
$start = $limit*$page - $limit;

// if for some reasons start position is negative set it to 0
// typical case is that the user type 0 for the requested page
if($start <0) $start = 0;

// the actual query for the grid data
$query="SELECT no_requisicion,";
$query.="desc_area_solicitante as area_solicitante,";
$query.="DATE_FORMAT(fec_solicitud,'%d/%m/%Y') as fec_solicitud,";
$query.="desc_cargo_solicitante as cargo_solicitante ";
$query.="FROM requisicion_p,area_solicitante,cargo_solicitante ";
$query.="WHERE no_area_solicitante=area_solicitante ";
$query.="AND no_cargo_solicitante=cargo_solicitante ";
$query.="ORDER BY $sidx $sord LIMIT $start,$limit";
$result = mysql_query( $query ) or die("No se puede ejecutar la sentencia.".mysql_error());

// constructing a JSON
$response->page = $page;
$response->total = $total_pages;
$response->records = $count;
$i=0;
while($row = mysql_fetch_array($result,MYSQL_ASSOC)) {
$response->rows[$i]['no_requisicion']=$row[no_requisicion];
$response->rows[$i]['cell']=array($row[no_requisicion],$row[area_solicitante],$row[fec_solicitud],$row[cargo_solicitante]);
$i++;
}

//Cierra la conexión
$Conexion->Close();

// return the formated data
echo $json->encode($response);
?>

This is Detail PHP code,

<?php
include_once ("conexion.php");

// to the url parameter are added 4 parameters as described in colModel
// we should get these parameters to construct the needed query
// Since we specify in the options of the grid that we will use a GET method
// we should use the appropriate command to obtain the parameters.
// In our case this is $_GET. If we specify that we want to use post
// we should use $_POST. Maybe the better way is to use $_REQUEST, which
// contain both the GET and POST variables. For more information refer to php documentation.
// Get the requested page. By default grid sets this to 1.
include("php/JSON.php");

$json = new Services_JSON();

$page = $_GET['page'];

// get how many rows we want to have into the grid - rowNum parameter in the grid
$limit = $_GET['rows'];

// get index row - i.e. user click to sort. At first time sortname parameter -
// after that the index from colModel
$sidx = $_GET['sidx'];

// sorting order - at first time sortorder
$sord = $_GET['sord'];

// if we not pass at first time index use the first column for the index or what you want
if(!$sidx) $sidx =1;

//Conexión a MySQL y a la BD
$Conexion=new Conexion();
$Conexion->getConexion();

// calculate the number of rows for the query. We need this to paging the result
$no_requisicion = (isset($_REQUEST['id']) ? trim($_REQUEST['id'] ): null);
if ($no_requisicion!=null){
$result = mysql_query("SELECT COUNT(*) AS count FROM requisicion_h WHERE no_requisicion = $no_requisicion");
}
else{
$result = mysql_query("SELECT COUNT(*) AS count FROM requisicion_h");
}
$row = mysql_fetch_array($result,MYSQL_ASSOC);
$count = $row['count'];

// calculate the total pages for the query
if( $count > 0 && $limit > 0) {
$total_pages = ceil($count/$limit);
} else {
$total_pages = 0;
}

// if for some reasons the requested page is greater than the total
// set the requested page to total page
if ($page > $total_pages) $page=$total_pages;

// calculate the starting position of the rows
$start = $limit*$page - $limit; // do not put $limit*($page - 1)

// if for some reasons start position is negative set it to 0
// typical case is that the user type 0 for the requested page
if ($start<0) $start = 0;

// the actual query for the grid data
$query="SELECT no_prog,desc_articulo as articulo,desc_unidad_medida as unidad_medida,solicitado,precio as costo_unitario, ";
$query.="solicitado*precio as costo_total ";
$query.="FROM requisicion_h,articulos,unidad_medida ";
$query.="WHERE articulo=no_articulo ";
$query.="AND unidad_medida=no_unidad_medida ";

if ($no_requisicion!=null){
$query.="AND no_requisicion=$no_requisicion ";
}
$query.="ORDER BY $sidx $sord LIMIT $start, $limit";
$result = mysql_query($query) or die("No se puede ejecutar la sentencia.".mysql_error());

// constructing a JSON
$response->page = $page;
$response->total = $total_pages;
$response->records = $count;
$i=0;
while($row = mysql_fetch_array($result,MYSQL_ASSOC)) {
$response->rows[$i]['no_prog']=$row[no_prog];
$response->rows[$i]['cell']=array($row[no_prog],$row[articulo],$row[unidad_medida],$row[solicitado],$row[costo_unitario],$row[costo_total]);
$i++;
}

//Cierra la conexión
$Conexion->Close();

// return the formated data
echo $json->encode($response);
?>

Thanks a lot