CSV Download from WordPress

<?php

/* Template Name: Download Data */

global $wpdb;

$sqlcon = '';
$sqlj = '';

$pageNum = isset($_GET['pagen']) ? $_GET['pagen'] : 1;
$previousRows = ($pageNum - 1) * 500;

$totalRecord = "";

if (!empty($_GET['catex'])) {
    if ($_GET['catex'] != -1) {
        $sqlcon = "
        AND tt.taxonomy = 'category'
        AND t.term_id = '" . intval($_GET['catex']) . "'";
    } else {
        $sqlcon = "
        AND tt.taxonomy = 'category'
        AND t.term_id != '65'";
        $totalRecord = "";
    }

    $sqlj = "
    JOIN $wpdb->term_relationships tr ON (p.ID = tr.object_id)
    JOIN $wpdb->term_taxonomy tt ON (tr.term_taxonomy_id = tt.term_taxonomy_id)
    JOIN $wpdb->terms t ON (tt.term_id = t.term_id)";
}

$querystr = "SELECT 
ID, post_title AS title, post_modified 
FROM $wpdb->posts p  
$sqlj 
WHERE p.post_type = 'post' AND p.post_status = 'publish' 
$sqlcon 
ORDER BY post_date DESC 
$totalRecord";

$pageposts = $wpdb->get_results($querystr, OBJECT);

// Prepare the output for CSV
header('Content-Type: application/csv');
header('Content-Disposition: attachment; filename="post_report_data.csv";');

$output = fopen('php://output', 'w');

// Add CSV header
fputcsv($output, ['Title', 'Url', 'Feature Image Url', 'Category', 'Revision Date', 'Meta Description']);

// Fetch and write each post's data directly
foreach ($pageposts as $post) {
    $url = wp_get_attachment_url(get_post_thumbnail_id($post->ID), 'thumbnail');
    $categories = implode(', ', array_map(function ($cat) {
        return $cat->cat_name;
    }, get_the_category($post->ID)));

    fputcsv($output, [
        $post->title,
        get_permalink($post->ID),
        $url,
        $categories,
        get_the_modified_date('Y-m-d H:i:s', $post->ID),
        get_post_meta($post->ID, '_yoast_wpseo_metadesc', true)
    ]);
}

fclose($output);
exit;