如何循环回显变量？

I currently tried this:

$custom_image = usp_get_meta(false, 'usp-custom-4');
$custom_image = htmlspecialchars_decode($custom_image);
$custom_image = nl2br($custom_image);
$custom_image = preg_replace('/<br \/>/iU', '', $custom_image);
foreach($custom_image as $img) {
    echo $img;
}

But I get

Warning: Invalid argument supplied for foreach() in...

Just an simple assumption to get it fixed:

Change $custom_image = preg_replace('/<br \/>/iU', '', $custom_image);

to $custom_image = explode('<br />',$custom_image);

Then you can loop it.