diff --git a/src/wp-includes/compat.php b/src/wp-includes/compat.php
index 9632afc842..c11e2d51a9 100644
--- a/src/wp-includes/compat.php
+++ b/src/wp-includes/compat.php
@@ -289,53 +289,6 @@ function _hash_hmac( $algo, $data, $key, $raw_output = false ) {
 	return $hmac;
 }
 
-if ( ! function_exists( 'json_encode' ) ) {
-	function json_encode( $string ) {
-		global $wp_json;
-
-		if ( ! ( $wp_json instanceof Services_JSON ) ) {
-			require_once( ABSPATH . WPINC . '/class-json.php' );
-			$wp_json = new Services_JSON();
-		}
-
-		return $wp_json->encodeUnsafe( $string );
-	}
-}
-
-if ( ! function_exists( 'json_decode' ) ) {
-	/**
-	 * @global Services_JSON $wp_json
-	 * @param string $string
-	 * @param bool   $assoc_array
-	 * @return object|array
-	 */
-	function json_decode( $string, $assoc_array = false ) {
-		global $wp_json;
-
-		if ( ! ( $wp_json instanceof Services_JSON ) ) {
-			require_once( ABSPATH . WPINC . '/class-json.php' );
-			$wp_json = new Services_JSON();
-		}
-
-		$res = $wp_json->decode( $string );
-		if ( $assoc_array ) {
-			$res = _json_decode_object_helper( $res );
-		}
-		return $res;
-	}
-
-	/**
-	 * @param object $data
-	 * @return array
-	 */
-	function _json_decode_object_helper( $data ) {
-		if ( is_object( $data ) ) {
-			$data = get_object_vars( $data );
-		}
-		return is_array( $data ) ? array_map( __FUNCTION__, $data ) : $data;
-	}
-}
-
 if ( ! function_exists( 'hash_equals' ) ) :
 	/**
 	 * Timing attack safe string comparison
@@ -373,85 +326,6 @@ if ( ! function_exists( 'hash_equals' ) ) :
 	}
 endif;
 
-// JSON_PRETTY_PRINT was introduced in PHP 5.4
-// Defined here to prevent a notice when using it with wp_json_encode()
-if ( ! defined( 'JSON_PRETTY_PRINT' ) ) {
-	define( 'JSON_PRETTY_PRINT', 128 );
-}
-
-if ( ! function_exists( 'json_last_error_msg' ) ) :
-	/**
-	 * Retrieves the error string of the last json_encode() or json_decode() call.
-	 *
-	 * @since 4.4.0
-	 *
-	 * @internal This is a compatibility function for PHP <5.5
-	 *
-	 * @return bool|string Returns the error message on success, "No Error" if no error has occurred,
-	 *                     or false on failure.
-	 */
-	function json_last_error_msg() {
-		// See https://core.trac.wordpress.org/ticket/27799.
-		if ( ! function_exists( 'json_last_error' ) ) {
-			return false;
-		}
-
-		$last_error_code = json_last_error();
-
-		// Just in case JSON_ERROR_NONE is not defined.
-		$error_code_none = defined( 'JSON_ERROR_NONE' ) ? JSON_ERROR_NONE : 0;
-
-		switch ( true ) {
-			case $last_error_code === $error_code_none:
-				return 'No error';
-
-			case defined( 'JSON_ERROR_DEPTH' ) && JSON_ERROR_DEPTH === $last_error_code:
-				return 'Maximum stack depth exceeded';
-
-			case defined( 'JSON_ERROR_STATE_MISMATCH' ) && JSON_ERROR_STATE_MISMATCH === $last_error_code:
-				return 'State mismatch (invalid or malformed JSON)';
-
-			case defined( 'JSON_ERROR_CTRL_CHAR' ) && JSON_ERROR_CTRL_CHAR === $last_error_code:
-				return 'Control character error, possibly incorrectly encoded';
-
-			case defined( 'JSON_ERROR_SYNTAX' ) && JSON_ERROR_SYNTAX === $last_error_code:
-				return 'Syntax error';
-
-			case defined( 'JSON_ERROR_UTF8' ) && JSON_ERROR_UTF8 === $last_error_code:
-				return 'Malformed UTF-8 characters, possibly incorrectly encoded';
-
-			case defined( 'JSON_ERROR_RECURSION' ) && JSON_ERROR_RECURSION === $last_error_code:
-				return 'Recursion detected';
-
-			case defined( 'JSON_ERROR_INF_OR_NAN' ) && JSON_ERROR_INF_OR_NAN === $last_error_code:
-				return 'Inf and NaN cannot be JSON encoded';
-
-			case defined( 'JSON_ERROR_UNSUPPORTED_TYPE' ) && JSON_ERROR_UNSUPPORTED_TYPE === $last_error_code:
-				return 'Type is not supported';
-
-			default:
-				return 'An unknown error occurred';
-		}
-	}
-endif;
-
-if ( ! interface_exists( 'JsonSerializable' ) ) {
-	define( 'WP_JSON_SERIALIZE_COMPATIBLE', true );
-	/**
-	 * JsonSerializable interface.
-	 *
-	 * Compatibility shim for PHP <5.4
-	 *
-	 * @link https://secure.php.net/jsonserializable
-	 *
-	 * @since 4.4.0
-	 */
-	interface JsonSerializable {
-		// phpcs:ignore WordPress.NamingConventions.ValidFunctionName.MethodNameInvalid
-		public function jsonSerialize();
-	}
-}
-
 // random_int was introduced in PHP 7.0
 if ( ! function_exists( 'random_int' ) ) {
 	require ABSPATH . WPINC . '/random_compat/random.php';