User Contributed Notes

1. Skip to note 16 content

   
   memuller
   
   
   11 years ago
   

   You must log in to vote on the helpfulness of this noteVote results for this note: 59You must log in to vote on the helpfulness of this note

   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. 

   • “If $single is true, an empty string is returned. If $single is false, an empty array is returned.” This is not true anymore. For WordPress 5.2.2: If $single is true: if the meta value is scalar, null is returned; otherwise, an empty array is returned. If $single is false: if the meta value is scalar, an array containing one null element is returned; otherwise, an array containing one empty array is returned. Therefore, one can’t check if the key exists or not, in the case the meta value is an array, because it will return an empty array, whether the value is set or not.

     Alfredo Barbosa 7 years ago

2. Skip to note 17 content

   
   Ian Dunn
   
   
   9 years ago
   

   You must log in to vote on the helpfulness of this noteVote results for this note: 39You must log in to vote on the helpfulness of this note

   The best thing about this function is that you no longer need to use it 🙂

   Since r21559 (v3.5), you can just call $post->foo to fetch the equivalent of get_post_meta( $post->ID, 'foo', true ).

   You can even extend that to introduce dynamically-generated fields, so you can call echo esc_html( $post->bar ) instead of $bar = some_custom_logic( get_post_meta( $post->ID, 'bar', true ) ); echo esc_html( $bar ).

   This makes code a lot cleaner and more readable.

   add_filter( 'get_post_metadata', 'add_dynamic_post_meta', 10, 4 );
   
   /**
    * Add dynamically-generated "post meta" to `WP_Post` objects
    *
    * This makes it possible to access dynamic data related to a post object by simply referencing `$post->foo`.
    * That keeps the calling code much cleaner than if it were to have to do something like
    * `$foo = some_custom_logic( get_post_meta( $post->ID, 'bar', true ) ); echo esc_html( $foo )`.
    *
    * @param mixed  $value
    * @param int    $post_id
    * @param string $meta_key
    * @param int    $single   @todo handle the case where this is false
    *
    * @return mixed
    *      `null` to instruct `get_metadata()` to pull the value from the database
    *      Any non-null value will be returned as if it were pulled from the database
    */
   function add_dynamic_post_meta( $value, $post_id, $meta_key, $single ) {
   	$post = get_post( $post_id );
   
   	if ( 'page' != $post->post_type ) {
   		return $value;
   	}
   
   	switch ( $meta_key ) {
   		case 'verbose_page_template':
   			$value = "The page template is " . ( $post->_wp_page_template ?: 'not assigned' );
   			break;
   	}
   
   	return $value;
   }

   • If there are multiple values for the key “bar”, $post->bar will only return the first value. get_post_meta( get_the_ID(), 'bar') will return all the values for the key “bar”. Multiple values can be added to a key using the add_post_meta function. Values can be removed with delete_post_meta.

     John Dorner 6 years ago

   • I don’t think this is good advice. First, any classic Post Meta key (using dashes) will produce a fatal error. At least it’d have to be `$post->{‘my-post-meta’}`. Second, any post meta storing an array of data, will fail and return only the first item of the array, afaik. So, get_post_meta _is_ still the right thing to use when getting post meta, since post meta is _not_ post data, but… post meta.

     Anonymous User 3 years ago

3. Skip to note 18 content

   
   Codex
   
   
   11 years ago
   

   You must log in to vote on the helpfulness of this noteVote results for this note: 24You must log in to vote on the helpfulness of this note

   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;
   }

4. Skip to note 19 content

   
   Codex
   
   
   11 years ago
   

   You must log in to vote on the helpfulness of this noteVote results for this note: 21You must log in to vote on the helpfulness of this note

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

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

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

5. Skip to note 20 content

   
   Codex
   
   
   11 years ago
   

   You must log in to vote on the helpfulness of this noteVote results for this note: 10You must log in to vote on the helpfulness of this note

   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”.

   
   	<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>
   

6. Skip to note 21 content

   
   stijnjanmaat
   
   
   10 years ago
   

   You must log in to vote on the helpfulness of this noteVote results for this note: 9You must log in to vote on the helpfulness of this note

   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 ) )

7. Skip to note 22 content

   
   BjornW
   
   
   11 years ago
   

   You must log in to vote on the helpfulness of this noteVote results for this note: 6You must log in to vote on the helpfulness of this note

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

8. Skip to note 23 content

   
   Because Name Already Exists
   
   
   6 years ago
   

   You must log in to vote on the helpfulness of this noteVote results for this note: 6You must log in to vote on the helpfulness of this note

   When we calling for all post meta, it will returned array value:

   $post_metas = get_post_meta(get_the_ID());

   sample output:

   array(2) {
     ["_meta_key1"]=>
     array(1) {
       [0]=> "value1"
      }
     ["_meta_key2"]=>
     array(1) {
       [0]=> "val2"
      }
   }

   We can make it into string, array_column will resulting default array value into string, for sure we need array combine to re-form array key:

   $post_metas = get_post_meta(get_the_ID());
   $post_metas = array_combine(array_keys($post_metas), array_column($post_metas, '0'));

   now output will be like here:

   array(2) {
     ["_meta_key1"]=>
     string(6) "value1"
     ["_meta_key2"]=>
     string(4) "val2"
   }

9. Skip to note 24 content

   
   kommasri
   
   
   9 years ago
   

   You must log in to vote on the helpfulness of this noteVote results for this note: 3You must log in to vote on the helpfulness of this note

   Display single meta value using meta key

10. Skip to note 25 content

    
    BjornW
    
    
    11 years ago
    

    You must log in to vote on the helpfulness of this noteVote results for this note: 2You must log in to vote on the helpfulness of this note

    Post meta keys are case-sensitive

11. Skip to note 26 content

    
    Nadav Rotchild
    
    
    9 years ago
    

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    If the value of the $key parameter is falsy get_post_meta will return the entire post meta array, even if $single is set to true. for example:

    get_post_meta( $post_id, FALSE, TRUE); //Returns all the post meta fields as an array.
    get_post_meta( $post_id, '0', TRUE); //Will also return all the post meta fields as an array. 

12. Skip to note 27 content

    
    heshamadel
    
    
    7 years ago
    

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    Function The Retrieve a Number views in post
    

    /**
     Pass in function
    
    	1: PostID                      =>     use get_the_ID();
    	2: Meta Key Name               =>   'you can called anythings'
    	3: Get The Post Meta Field     =>   get_post_meta();
    	4: The Number Start Count      =>    add anyNumber ( 0,1,100,1000 or 2000 )
    	5: Count +1
    	6: Called Function in anypage  =>  
    
     but you should remove (adjacent_posts_rel_link_wp_head)
    **/
    
    	function relationscode_post_views( ) {
           $postID = get_the_ID();
    	   $metaKey = 'relationscode_post_views';
    	   $views = get_post_meta( $postID, $metaKey, true );
    	   $count_start_num = 0;
    	
    	   $count = ( empty( $views ) ? $count_start_num : $views );
           $count++;
        
           if(is_single()) {
        	  update_post_meta( $postID, $metaKey, $count );
        	  echo $count;
           } else {
        	   echo $views;
            
           }
    	
       }
       remove_action( 'wp_head', 'adjacent_posts_rel_link_wp_head', 10, 0 );
     

13. Skip to note 28 content

    
    Hay
    
    
    5 years ago
    

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    Note that to add or set post meta values you can use the function <a href="https://developer.wordpress.org/reference/functions/add_post_meta/">add_post_meta</a>:

    add_post_meta( $post_id, $meta_key, $value );

14. Skip to note 29 content

    
    Koen Reus
    
    
    5 years ago
    

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    Here’s a pitfall to steer clear of…

    register_post_meta() allows you to define a default value for a meta field. If the default value evaluates to true, you’ll be scratching your head why get_post_meta() returns true when you haven’t yet set a value, or just used delete_post_meta() .

    Obviously get_post_meta() will return the default value defined in register_post_meta() .

     true,
    	'type'		=> 'boolean',
    	'default'	=> true,
    ]);
    
    if(!get_post_meta($post_id, 'sample_field', true)){
    	//This will now always execute unless you manually update the sample_field meta to false
    }

15. Skip to note 30 content

    
    Mário Valney
    
    
    8 years ago
    

    You must log in to vote on the helpfulness of this noteVote results for this note: -1You must log in to vote on the helpfulness of this note

    False if post ID isn’t absint or is 0

    Passing $post_id == 0 (or anything not a absint) will return false no matter $single.

    $meta = get_post_meta( 0, 'key', true );
    var_dump( $meta ); // bool(false)
    
    $meta = get_post_meta( 0, 'key', false );
    var_dump( $meta ); // bool(false)

    • Just for the record, WordPress returns either empty string (”) or an empty array (is_countable and count === 0) when you attempt to retrieve a meta value using a post ID or meta key that doesn’t exist.

      Brian Layman 7 years ago