wp_json_encode() vs json_encode() in WordPress

Most WordPress developers use json_encode() without thinking about it. It usually works. But there's a reason WordPress ships its own wrapper.

The difference

json_encode() is native PHP. wp_json_encode() is a WordPress wrapper that does a few extra things.

PHP

// Native PHP
echo json_encode( $data );

// WordPress
echo wp_json_encode( $data );

On the surface, same output. Under the hood, not quite.

What wp_json_encode() actually does

First, it sets JSON_UNESCAPED_UNICODE by default. Native json_encode() escapes non-ASCII characters as `\uXXXX` sequences. This causes issues with Arabic, Hebrew, Chinese, or any non-Latin content.

PHP

$data = [ 'name' => 'محمد' ];

// json_encode output:
// {"name":"محمد"}

// wp_json_encode output:
// {"name":"محمد"}

Second, it handles encoding failures. If json_encode() fails on bad input, it returns false silently. wp_json_encode() returns false too, but it also triggers a _doing_it_wrong() notice in debug mode so you actually catch the problem.

Third, it strips invalid UTF-8 bytes before encoding. Native json_encode() will fail or produce garbage output on invalid UTF-8 strings. This happens more often than expected when dealing with user input, database content, or third-party API responses.

Real example

PHP

$data = [
    'title'   => get_the_title(),
    'content' => get_post_field( 'post_content', $post_id ),
];

// Risky: fails silently on bad characters
header( 'Content-Type: application/json' );
echo json_encode( $data );

// Safe: handles edge cases, consistent output
wp_send_json_success( $data ); // uses wp_json_encode internally

When it matters most

AJAX handlers returning post content or user input
Localizing data with wp_localize_script()
REST API custom endpoints
Any site with multilingual content

Practical rule

Inside WordPress, always use wp_json_encode() over json_encode(). If you're using wp_send_json_success() or wp_send_json_error(), you're already covered - they call wp_json_encode() internally.

One small habit. Fewer silent bugs.