export_csv.php

<?php
include_once implode(DIRECTORY_SEPARATOR, [__DIR__, 'conector.inc.php']);
const debug=true;
$format=$_GET['format']??'json';

if (debug){
    ini_set('display_errors', 1);
    ini_set('display_startup_errors', 1);
    error_reporting(E_ALL);
}

$params = [];
/*buscandod formatear parametros $_GET*/
$datos = implode($_GET," and ");
$output = implode(', ', array_map(
    function ($v, $k) {
        if(is_array($v)){
            return $k.'[]='.implode('&'.$k.'[]=', $v);
        }else{
            return $k.'='.$v;
        }
    },
    $_GET,
    array_keys($_GET)
));
foreach($_GET as $key=>$value){
    if (!empty($value)){
        if (strpos($value, ",")>0){

            $valores = explode(",", $value);
            $nuevos_valores = "";
            foreach($valores as $k){
                $nuevos_valores .= "'$k',";
            }
            $nuevos_valores = rtrim( $nuevos_valores,",");
            array_push($params, implode("",array($key => "$key in ($nuevos_valores)")));
        }else{
            array_push($params, implode("", array($key=>"$key='$value'")));
        }
    }
}
$output = implode( " and ", $params);
$c = get_conector_pdo();
$q = 'select dg.* from datos_generales dg where ' . $output;
if (!empty($output)){
    $r = $c->query($q);
}else{
    $r = $c->query('select * from datos_generales');
}

header('Content-Encoding: UTF-8');
header('Content-Type: text/csv;charset=UTF-8');
header('Content-Disposition: attachment; filename="export.csv"');
echo "\xEF\xBB\xBF";/*hacky ut8 boom*/

$data = $r->fetchAll(PDO::FETCH_ASSOC); //datatables require un item data con los valores de los campos
$header =true;
foreach($data as $row){
    if ($header){
        $h = array_keys($row);
        echo implode(";", $h) . PHP_EOL;
        $header = false;
    }
   echo implode(";", $row). PHP_EOL;
}
die();

export_json.php

<?php
include_once implode(DIRECTORY_SEPARATOR, [__DIR__, 'conector.inc.php']);
const debug=false;
if (debug){
    ini_set('display_errors', 1);
    ini_set('display_startup_errors', 1);
    error_reporting(E_ALL);
}
$params = [];
/*buscandod formatear parametros $_GET*/
$datos = implode($_GET," and ");
$output = implode(', ', array_map(
    function ($v, $k) {
        if(is_array($v)){
            return $k.'[]='.implode('&'.$k.'[]=', $v);
        }else{
            return $k.'='.$v;
        }
    },
    $_GET,
    array_keys($_GET)
));
foreach($_GET as $key=>$value){
    if (!empty($value)){
        if (strpos($value, ",")>0){
            $valores = explode(",", $value);
            $nuevos_valores = "";
            foreach($valores as $k){
                $nuevos_valores .= "'$k',";
            }
            $nuevos_valores = rtrim( $nuevos_valores,",");
            array_push($params, implode("",array($key => "$key in ($nuevos_valores)")));
        }else{
            array_push($params, implode("", array($key=>"$key='$value'")));
        }
    }
}
$output = implode( " and ", $params);
$c = get_conector_pdo();
$q = 'select dg.* from datos_generales dg where ' . $output;
if (!empty($output)){
    $r = $c->query($q);
}else{
    $r = $c->query('select * from datos_generales');
}
/*exportar datos*/
header('Content-Type: application/json;charset=utf-8');
$data = array("data"=>$r->fetchAll(PDO::FETCH_ASSOC)); //datatables require un item data con los valores de los campos
echo json_encode($data,JSON_UNESCAPED_UNICODE|JSON_PRETTY_PRINT);

Obs: los argumentos de la request se procesan para formar el WHERE de la consulta, este detecta los multvalores de los select multiple y genera el in (x,y....)