Converts Unicode Emojii to HTML Entities

emoji-to-html-entity.php

<?php
function to_unicode($text) {
    $str = preg_replace_callback(
        "%(?:\xF0[\x90-\xBF][\x80-\xBF]{2} | [\xF1-\xF3][\x80-\xBF]{3} | \xF4[\x80-\x8F][\x80-\xBF]{2})%xs",
        function($emoji){
            $emojiStr = mb_convert_encoding($emoji[0], 'UTF-32', 'UTF-8');
            return preg_replace("/^[0]+/","&#x",bin2hex($emojiStr) . ';');
        },
        $text
    );
    return $str;
}

echo to_unicode( 'hello world 💙' );
// hello world &#x1f499;