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get_metadata( string $meta_type, int $object_id, string $meta_key = '', bool $single = false ): mixed

Since
2.9.0
Source
wp-includes/meta.php:601
Retrieves the value of a metadata field for the specified object type and ID.

Description

If the meta field exists, a single value is returned if $single is true, or an array of values if it's false.

If the meta field does not exist, the result depends on get_metadata_default().
By default, an empty string is returned if $single is true, or an empty array if it's false.

Compatibility

WordPress
since 2.9.0
PHP
7.4–8.6-dev
  • 6.7.7
  • 6.8.8
  • 6.9.7
  • 7.0.4
  • 7.1.0

Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.

Parameters

$meta_typestring
Type of object metadata is for. Accepts 'blog', 'post', 'comment', 'term', 'user', or any other object type with an associated meta table.
$object_idint
ID of the object metadata is for.
$meta_keystringoptional
Metadata key. If not specified, retrieve all metadata for the specified object. Default empty string.Default: ''
$singlebooloptional
If true, return only the first value of the specified $meta_key.
This parameter has no effect if $meta_key is not specified. Default false.Default: false

Return value

mixed
An array of values if $single is false.
The value of the meta field if $single is true.
False for an invalid $object_id (non-numeric, zero, or negative value), or if $meta_type is not specified.
An empty array if a valid but non-existing object ID is passed and $single is false.
An empty string if a valid but non-existing object ID is passed and $single is true.
Note: Non-serialized values are returned as strings:
- false values are returned as empty strings ('')
- true values are returned as '1'
- numbers (both integer and float) are returned as strings Arrays and objects retain their original type.

Performance profile

How much work a call to get_metadata() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.

Cost class
Light

Only touches the object cache, via wp_cache_get().

Scaling
Constant

No loop in the body: the same number of instructions runs whatever you pass in.

Instructions
14–20

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 21.

Plugin surface
None

Nothing here hands control to plugin code.

Called by
9

9 places in core call this, so the cost is paid more often than your own code shows.

What it touches

  • hookthird-party callbacksapply_filters()one call below get_metadata()
  • cacheobject cachewp_cache_get()one call below get_metadata()
  • serializeserialisationmaybe_unserialize()one call below get_metadata()

What one call costs · 2 distinct outcomes

One number would be a lie: the work depends on which branch runs. These are every distinct cost get_metadata() can have, taken from its control-flow graph on PHP 8.5.

WhenInstructionsCalls it makes
$value !== null14get_metadata_raw()
$value === null20get_metadata_raw(), get_metadata_default()

Across PHP versions

Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 21 instructions, 14–20 executed per call, 1 branch. The work does not change between versions.

An instruction is not a fixed amount of time, so a matching count is not necessarily the same speed; what it rules out is a difference in the work itself.

Uses · 2

Used by · 9

Source code

View on Trac View on GitHub 

function get_metadata( $meta_type, $object_id, $meta_key = '', $single = false ) {	$value = get_metadata_raw( $meta_type, $object_id, $meta_key, $single );	if ( ! is_null( $value ) ) {		return $value;	} 	return get_metadata_default( $meta_type, $object_id, $meta_key, $single );}

Changelog

Introduced in 2.9.0. Unchanged from 6.7.7 through 7.1.0.

  1. 6.7.7
  2. 6.8.8
  3. 6.9.7
  4. 7.0.4
  5. 7.1.0

Signature, return type and hooks compared across 5 parsed releases.

About this page

Parsed data
Generated from the wordpress-develop 7.1.0 tag, from src/wp-includes/meta.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.
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