_wp_json_convert_string() │ WP 4.1.0

Converts a string to UTF-8, so that it can be safely encoded to JSON.

Internal function — this function is designed to be used by the kernel itself. It is not recommended to use this function in your code.

No Hooks.

Return

String. The checked string.

Usage

_wp_json_convert_string( $input_string );
$input_string(string) (required)
The string which is to be converted.

Notes

Changelog

Since 4.1.0 Introduced.

_wp_json_convert_string() code WP 6.5.2

wp-includes/functions.php 
function _wp_json_convert_string( $input_string ) {
	static $use_mb = null;
	if ( is_null( $use_mb ) ) {
		$use_mb = function_exists( 'mb_convert_encoding' );
	}

	if ( $use_mb ) {
		$encoding = mb_detect_encoding( $input_string, mb_detect_order(), true );
		if ( $encoding ) {
			return mb_convert_encoding( $input_string, 'UTF-8', $encoding );
		} else {
			return mb_convert_encoding( $input_string, 'UTF-8', 'UTF-8' );
		}
	} else {
		return wp_check_invalid_utf8( $input_string, true );
	}
}