add_action('init', function() {
    if (!isset($_GET['delete_posts'])) return;

    global $wpdb;

    $batch = 5000;

    $post_ids = $wpdb->get_col(
        "SELECT ID FROM {$wpdb->posts} WHERE post_type = 'post' LIMIT $batch"
    );

    if (empty($post_ids)) {
        echo "Done.";
        exit;
    }

    $ids_str = implode(',', array_map('intval', $post_ids));

    $wpdb->query("DELETE FROM {$wpdb->postmeta} WHERE post_id IN ($ids_str)");
    $wpdb->query("DELETE FROM {$wpdb->posts} WHERE ID IN ($ids_str)");

    echo count($post_ids) . " posts deleted.";
    exit;
});
<br />
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<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /home/standa9/public_html/wp-content/mu-plugins/index.php:1) in <b>/home/standa9/public_html/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1831</b><br />
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(2)"},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","template":"","meta":{"_uag_custom_page_level_css":"","site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}}},"happyfiles_category":[10],"description":{"rendered":"<p class=\"attachment\"><a href='https:\/\/ibomberdefense.standardof.net\/wp-content\/uploads\/sites\/5\/2020\/10\/iBomber-Defense-Level-2-Western-Mediterranean-Sea-Devils-2.jpg'><img decoding=\"async\" width=\"512\" height=\"288\" src=\"https:\/\/ibomberdefense.standardof.net\/wp-content\/uploads\/sites\/5\/2020\/10\/iBomber-Defense-Level-2-Western-Mediterranean-Sea-Devils-2-512x288.jpg\" class=\"attachment-medium size-medium\" alt=\"&quot;iBomber Defense&quot; - Level 2 - Western Mediterranean: Sea Devils! (2)\" srcset=\"https:\/\/ibomberdefense.standardof.net\/wp-content\/uploads\/sites\/5\/2020\/10\/iBomber-Defense-Level-2-Western-Mediterranean-Sea-Devils-2-512x288.jpg 512w, https:\/\/ibomberdefense.standardof.net\/wp-content\/uploads\/sites\/5\/2020\/10\/iBomber-Defense-Level-2-Western-Mediterranean-Sea-Devils-2-800x450.jpg 800w, https:\/\/ibomberdefense.standardof.net\/wp-content\/uploads\/sites\/5\/2020\/10\/iBomber-Defense-Level-2-Western-Mediterranean-Sea-Devils-2-200x113.jpg 200w, https:\/\/ibomberdefense.standardof.net\/wp-content\/uploads\/sites\/5\/2020\/10\/iBomber-Defense-Level-2-Western-Mediterranean-Sea-Devils-2-768x432.jpg 768w, https:\/\/ibomberdefense.standardof.net\/wp-content\/uploads\/sites\/5\/2020\/10\/iBomber-Defense-Level-2-Western-Mediterranean-Sea-Devils-2-16x9.jpg 16w, https:\/\/ibomberdefense.standardof.net\/wp-content\/uploads\/sites\/5\/2020\/10\/iBomber-Defense-Level-2-Western-Mediterranean-Sea-Devils-2.jpg 1280w\" sizes=\"(max-width: 512px) 100vw, 512px\" \/><\/a><\/p>\n<p>Wave 10 turret placement.<\/p>\n"},"caption":{"rendered":"<p>Wave 10 turret placement.<\/p>\n"},"alt_text":"\"iBomber Defense\" - Level 2 - Western Mediterranean: Sea Devils! 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