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   Contributed by Codex — 1 year ago

   Show the first value of the specified key inside a loop

   $key_1_value = get_post_meta( get_the_ID(), 'key_1', true );
   // Check if the custom field has a value.
   if ( ! empty( $key_1_value ) ) {
   	echo $key_1_value;
   }
   

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   Contributed by Codex — 1 year ago

   Default Usage
   Get the meta for all keys for the current post:

   <?php $meta = get_post_meta( get_the_ID() ); ?>
   

   Get all meta for a single key for the current post:

   <?php $key_1_values = get_post_meta( get_the_ID(), 'key_1' ); ?>
   

   Get the first value of a meta key for the current post:

   <?php $key_1_value = get_post_meta( get_the_ID(), 'key_1', true ); ?>
   

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   Contributed by memuller — 1 year ago

   Return values when no meta field is found
   If a meta field with the given $key isn’t found for the given $post_id, the return value varies:

   If $single is true, an empty string is returned.
   If $single is false, an empty array is returned.

   Since both evaluate as false, you can use get_post_meta directly in conditionals, like this:

   if( ! get_post_meta( '1', 'non-existing_meta', true ) ) {}
   if( ! get_post_meta( '1', 'non-existing_meta', false ) ) {}
   // both ifs will get run if no meta field is found; since
   // array() == false and '' == false
   

   What if I want to store an empty string?
   If for some reason your with to store an empty string or array into your meta field, get_post_meta will not be reliable when checking if the given meta field exists.
   In this case, you can use get_post_custom_keys to do so:

   if( ! in_array( 'given_key', get_post_custom_keys( '1' ) ) ) {} 
   // this correctly checks for the existence of the given key, 
   // even if it's empty or has a value that evaluates as false. 
   

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   Contributed by BjornW — 1 year ago

   If you want to hide postmeta keys from the customfields prefix the key name with an underscore.

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   Contributed by Codex — 1 year ago

   Retrieve a Custom Field Thumbnail Url
   While you are in the WordPress Loop, you can use this code to retrieve a custom field. In this example, the thumbnail image url is in a custom field named “thumb”.

   <?php if ( get_post_meta( get_the_ID(), 'thumb', true ) ) : ?>
   	<a href="<?php the_permalink() ?>" rel="bookmark">
   		<img class="thumb" src="<?php echo esc_url( get_post_meta( get_the_ID(), 'thumb', true ) ); ?>" alt="<?php the_title_attribute(); ?>" />
   	</a>
   <?php endif; ?>
   

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   Contributed by BjornW — 1 year ago

   Post meta keys are case-sensitive

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   Contributed by stijnjanmaat — 2 months ago

   When you don’t specify a $key (”) and set $single to true in get_post_meta, it will return all keys still with an array of values.

   $meta = get_post_meta(get_the_ID(), '', true);
   print_r($meta);
   //Array ( [key_1] => Array ( [0] => value_1 ), [key_2] => Array ( [0] => value_2 ) )
   

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   Contributed by sltmunky69 — 3 months ago

   When I had tons of meta keys to work with to display some custom content for custom post types, instead of making several dozen calls to the get_post_meta function to grab the keys I wanted, I wrote this function instead. Basically it gets all of the meta keys and filters out all of the arrays with single values while maintaining any arrays that actually do have multiple values and returns an associative array of the results. If you have lots of single values to get, it saves you from having to iterate over every result to get your $k=>$v pairs so you can just access them by $mk[‘my_custom_meta_key’].
   function array_push_assoc($array, $key, $value){
$array[$key] = $value;
return $array;
}

   function filter_gpm($array){
$mk = array();
foreach($array as $k => $v){
if(is_array($v) && count($v) == 1){
$mk = array_push_assoc($mk, $k, $v[0]);
} else {
$mk = array_push_assoc($mk, $k, $v);
}
}
return $mk;
}
   Call it like so
   $mk = filter_gpm( get_post_meta( get_the_ID() ) );

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