Php 7.4 and WP supercache

did you ever find a solutions. i having this issue as well

Why don’t you rollback to php 7.3? I had this issue and fixed this by switching back to php 7.3!

Its easy to fix these errors one by one untill you fix them all, just search for every error message on Google and you will be able to edit the code, unfortunately I don’t have time for upgrading to php 7.4 and fixing all other plugins errors!

but i did figure it out
starting at line 3712 just copy and paste

add_filter( 'option_preload_cache_counter', 'option_preload_cache_counter' );

function check_up_on_preloading() {
	$value = get_option( 'preload_cache_counter' );
	if ( is_array($value) && $value[ 'c' ] > 0 && ( time() - $value[ 't' ] ) > 3600 && false == wp_next_scheduled( 'wp_cache_preload_hook' ) ) {
		if ( is_admin() ) {
			if ( get_option( 'wpsc_preload_restart_email' ) < ( time() - 86400 ) ) {
				wp_mail( get_option( 'admin_email' ), sprintf( __( '[%s] Preload may have stalled.', 'wp-super-cache' ), get_bloginfo( 'url' ) ), sprintf( __( "Preload has been restarted.\n%s", 'wp-super-cache' ), admin_url( "options-general.php?page=wpsupercache" ) ) );
				update_option( 'wpsc_preload_restart_email', time() );
			}
			add_action( 'admin_notices', 'wpsc_preload_restart_notice' );
		}
		wp_schedule_single_event( time() + 30, 'wp_cache_preload_hook' );
	}
}