How to get custom field value in WordPress

How to get custom field value in WordPress

<?php
$zip_code = get_post_meta($post->ID, "zipcode", true);
echo $zip_code;
?>

Get image url of custom file field

$client_image_url = '';
if(get_post_meta($query[$i]->ID, 'client_image', true)){

$client_image = get_page(get_post_meta($query[$i]->ID, 'client_image', true));
$client_image_url = $client_image->guid;

}
and display image:

<?php if(!empty($client_image_url)){
echo '<img src="'.$client_image_url.'"/>';
}
?>