Help with this custom field conditional if no field is set display nothing

Question

I'm using the code below to display an image if the swap_select custom field value is true. If it's no it displays nothing. However when posts are first created no custom field exists. So what would the conditional be to account for no custom field at all and in that case display noithing?

<?php 
$swap_value = get_post_meta($post->ID, 'swap_select', true);
// check if the custom field has a value
if($swap_value!= 'no') {
  echo '<img class="" src="thumbs/speechbubble_pink.png"/>';
}
else{
}
?>

Answer 1

I prefer empty for this because it considers a lot of things to be "empty" besides just an empty string, and that is the behavior I usually want. Be aware of that though.

I am not 100% sure what you are doing but...

if( empty($swap_value) ) {
  // runs if no $swap_value, or an empty value
}
// OR
if( !empty($swap_value) ) {
  // runs if $swap_value is set to something
}

Reference the PHP Docs for exactly what empty considers "empty" or "not empty".