wppaste
WordPress

wp_send_json_error( mixed $value = null, int $status_code = null, int $flags = 0 )

Since
3.5.0, 4.1.0, 4.7.0, 5.6.0
Source
wp-includes/functions.php:4587

Terminates the current Ajax request by outputting a JSON object with success set to false and an optional data payload built from $value. If $value is a WP_Error, its codes and messages are flattened into an array before output; any other type is passed through unchanged. Because it calls wp_send_json() internally, nothing after the call executes, so pair it with wp_send_json_success() for the matching happy path.

Sends a JSON response back to an Ajax request, indicating failure.

Description

If the $value parameter is a WP_Error object, the errors within the object are processed and output as an array of error codes and corresponding messages. All other types are output without further processing.

Compatibility

WordPress
since 5.6.0
PHP
7.4–8.6-dev
  • 6.7.10
  • 6.8.11
  • 6.9.10
  • 7.0.7
  • 7.1.3

Present in every tracked release (6.7.10 to 7.1.3), and compiles on PHP 7.4 through 8.6-dev.

Parameters

$valuemixedoptional
Data to encode as JSON, then print and die. Default null.Default: null
$status_codeintoptional
The HTTP status code to output. Default null.Default: null
$flagsintoptional
Options to be passed to json_encode(). Default 0.Default: 0

Code examples

Every example is editable and runs in a real WordPress booted in your browser by WordPress Playground. Press Run, then edit the code: clicking away re-runs it. Nothing is sent anywhere until you do.

Send a JSON error when an Ajax request references a missing post

A minimal Ajax-style check against a post ID that does not exist in the baseline data.

$requested_id = 99;

if ( ! get_post( $requested_id ) ) {
	wp_send_json_error( array( 'message' => sprintf( 'Post %d does not exist.', $requested_id ) ) );
}

echo esc_html( 'Post found, continuing.' );

wp_send_json_error() dies after printing, so the final echo only runs on the success path.

Return WP_Error details from a price validation Ajax handler

Validate a submitted price against the existing price meta on post 2 and report every problem at once.

$post_id = 2;
$submitted_price = 'not-a-number';
$errors = new WP_Error();

if ( ! is_numeric( $submitted_price ) ) {
	$errors->add( 'invalid_price', 'The submitted price must be numeric.' );
}

if ( ! metadata_exists( 'post', $post_id, 'price' ) ) {
	$errors->add( 'missing_price_meta', 'This post has no existing price to update.' );
}

if ( $errors->has_errors() ) {
	wp_send_json_error( $errors );
}

update_post_meta( $post_id, 'price', $submitted_price );
echo esc_html( 'Price updated.' );

Each WP_Error code/message pair becomes its own array entry in the JSON 'data' field, so multiple problems can be reported in one response.

Common problems and fixes · 4

Why does none of my code after wp_send_json_error() run?

The function's last line calls wp_send_json(), which prints the JSON and calls wp_die(). Execution stops there by design, so any code below the call in the same request is never reached.

Why is response.data undefined in my JS success callback?

Looking at the source, the 'data' key is only added when isset( $value ) is true. Calling wp_send_json_error() with no argument, or with an explicit null, produces a response containing only success: false and no data key at all.

Why did the extra data I attached to my WP_Error disappear?

The function only reads $value->errors, pulling out each error code and its message text. Anything attached with WP_Error::add_data() lives on a separate error_data property that this function never touches, so it never reaches the JSON response.

Why do I get a 'headers already sent' warning when I call this function?

wp_send_json_error() hands off to wp_send_json(), which sets the Content-Type header before printing. If your code has already echoed HTML, whitespace, or a PHP notice earlier in the request, that header call fails.

Alternatives and related functions

wp_send_json_success
When the Ajax request succeeded and you need the matching response with success set to true.
wp_send_json
When you need full control over the response array's shape instead of the fixed success/data structure this function builds.
WP_Error
When you need to collect one or more error codes and messages before passing them as $value.
is_wp_error
When you want to branch on whether a value is an error object before deciding how to build the response yourself.

Performance profile

How much work a call to wp_send_json_error() 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
Heavy

Reads stored settings via get_option(), cached per request but not free on a cold cache.

Scaling
Scales with input

The body loops, so the work grows with what you pass in.

Instructions
12–24

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 36.

Plugin surface
None

Nothing here hands control to plugin code.

Called by
50

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

What it touches

  • hookthird-party callbacksdo_action()one call below wp_send_json_error()
  • optionoption read or writeget_option()one call below wp_send_json_error()

Further down the call graph this can also reach cache, serialize, query and transient. Those are the worst case, several calls deep and usually down an error path, not what a normal call pays.

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 wp_send_json_error() can have, taken from its control-flow graph on PHP 8.5.

WhenInstructionsCalls it makes
!isset($value)12wp_send_json()
isset($value)18–24is_wp_error(), wp_send_json()

Across PHP versions

Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 36 instructions, 12–24 executed per call, 6 branches. 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 · 50

Show all 50

Source code

View on Trac View on GitHub 

function wp_send_json_error( $value = null, $status_code = null, $flags = 0 ) {	$response = array( 'success' => false ); 	if ( isset( $value ) ) {		if ( is_wp_error( $value ) ) {			$result = array();			foreach ( $value->errors as $code => $messages ) {				foreach ( $messages as $message ) {					$result[] = array(						'code'    => $code,						'message' => $message,					);				}			} 			$response['data'] = $result;		} else {			$response['data'] = $value;		}	} 	wp_send_json( $response, $status_code, $flags );}

Changelog

Introduced in 3.5.0. One change between 6.7.10 and 7.1.3.

  1. 6.7.10
  2. 6.8.11
  3. 6.9.10
  4. 7.0.7
  5. 7.1.3

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

7.1.3
Return type changed from none to never.verified against source
5.6.0
The $flags parameter was added.from the docblock
4.7.0
The $status_code parameter was added.from the docblock
4.1.0
The $value parameter is now processed if a WP_Error object is passed in.from the docblock
3.5.0
Introduced.from the docblock

About this page

Parsed data
Generated from the wordpress-develop 6.7.10 tag, from src/wp-includes/functions.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.
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