src/EmojiModifier.php
private function utf8ToUnicode($str)
    {
        $mState = 0;     // cached expected number of octets after the current octet
                         // until the beginning of the next UTF8 character sequence
        $mUcs4  = 0;     // cached Unicode character
        $mBytes = 1;     // cached expected number of octets in the current sequence

        $out = array();

        $len = strlen($str);
        for($i = 0; $i < $len; $i++) {
            $in = ord($str{$i});
            if (0 == $mState) {
                // When mState is zero we expect either a US-ASCII character or a
                // multi-octet sequence.
                if (0 == (0x80 & ($in))) {
                    // US-ASCII, pass straight through.
                    $out[] = $in;
                    $mBytes = 1;
                } else if (0xC0 == (0xE0 & ($in))) {
                    // First octet of 2 octet sequence
                    $mUcs4 = ($in);
                    $mUcs4 = ($mUcs4 & 0x1F) << 6;
                    $mState = 1;
                    $mBytes = 2;
                } else if (0xE0 == (0xF0 & ($in))) {
                    // First octet of 3 octet sequence
                    $mUcs4 = ($in);
                    $mUcs4 = ($mUcs4 & 0x0F) << 12;
                    $mState = 2;
                    $mBytes = 3;
                } else if (0xF0 == (0xF8 & ($in))) {
                    // First octet of 4 octet sequence
                    $mUcs4 = ($in);
                    $mUcs4 = ($mUcs4 & 0x07) << 18;
                    $mState = 3;
                    $mBytes = 4;
                } else if (0xF8 == (0xFC & ($in))) {
                    /* First octet of 5 octet sequence.
                     *
                     * This is illegal because the encoded codepoint must be either
                     * (a) not the shortest form or
                     * (b) outside the Unicode range of 0-0x10FFFF.
                     * Rather than trying to resynchronize, we will carry on until the end
                     * of the sequence and let the later error handling code catch it.
                     */
                    $mUcs4 = ($in);
                    $mUcs4 = ($mUcs4 & 0x03) << 24;
                    $mState = 4;
                    $mBytes = 5;
                } else if (0xFC == (0xFE & ($in))) {
                    // First octet of 6 octet sequence, see comments for 5 octet sequence.
                    $mUcs4 = ($in);
                    $mUcs4 = ($mUcs4 & 1) << 30;
                    $mState = 5;
                    $mBytes = 6;
                } else {
                    /* Current octet is neither in the US-ASCII range nor a legal first
                     * octet of a multi-octet sequence.
                     */
                    return false;
                }
            } else {
                // When mState is non-zero, we expect a continuation of the multi-octet
                // sequence
                if (0x80 == (0xC0 & ($in))) {
                    // Legal continuation.
                    $shift = ($mState - 1) * 6;
                    $tmp = $in;
                    $tmp = ($tmp & 0x0000003F) << $shift;
                    $mUcs4 |= $tmp;

                    if (0 == --$mState) {
                        /* End of the multi-octet sequence. mUcs4 now contains the final
                         * Unicode codepoint to be output
                         *
                         * Check for illegal sequences and codepoints.
                         */

                        // From Unicode 3.1, non-shortest form is illegal
                        if (((2 == $mBytes) && ($mUcs4 < 0x0080)) ||
                          ((3 == $mBytes) && ($mUcs4 < 0x0800)) ||
                          ((4 == $mBytes) && ($mUcs4 < 0x10000)) ||
                          (4 < $mBytes) ||
                          // From Unicode 3.2, surrogate characters are illegal
                          (($mUcs4 & 0xFFFFF800) == 0xD800) ||
                          // Codepoints outside the Unicode range are illegal
                          ($mUcs4 > 0x10FFFF)) {
                            return false;
                        }
                        if (0xFEFF != $mUcs4) {
                            // BOM is legal but we don't want to output it
                            $out[] = $mUcs4;
                        }
                        //initialize UTF8 cache
                        $mState = 0;
                        $mUcs4  = 0;
                        $mBytes = 1;
                    }
                } else {
                    /* ((0xC0 & (*in) != 0x80) && (mState != 0))
                     *
                     * Incomplete multi-octet sequence.
                     */
                    return false;
                }
            }
        }

        //this bit is mine, to return as U+XXXX...
        $return = '';
        foreach ($out as $num) {
            $return .= 'U+' . str_pad(dechex($num), 4, '0', STR_PAD_LEFT) . ' ';
        }
        $return = strtoupper(rtrim($return));

        return $return;
    }
private function utf8ToUnicode($str)
    {
        $mState = 0;     // cached expected number of octets after the current octet
                         // until the beginning of the next UTF8 character sequence
        $mUcs4  = 0;     // cached Unicode character
        $mBytes = 1;     // cached expected number of octets in the current sequence

        $out = array();

        $len = strlen($str);
        for($i = 0; $i < $len; $i++) {
            $in = ord($str{$i});
            if (0 == $mState) {
                // When mState is zero we expect either a US-ASCII character or a
                // multi-octet sequence.
                if (0 == (0x80 & ($in))) {
                    // US-ASCII, pass straight through.
                    $out[] = $in;
                    $mBytes = 1;
                } else if (0xC0 == (0xE0 & ($in))) {
                    // First octet of 2 octet sequence
                    $mUcs4 = ($in);
                    $mUcs4 = ($mUcs4 & 0x1F) << 6;
                    $mState = 1;
                    $mBytes = 2;
                } else if (0xE0 == (0xF0 & ($in))) {
                    // First octet of 3 octet sequence
                    $mUcs4 = ($in);
                    $mUcs4 = ($mUcs4 & 0x0F) << 12;
                    $mState = 2;
                    $mBytes = 3;
                } else if (0xF0 == (0xF8 & ($in))) {
                    // First octet of 4 octet sequence
                    $mUcs4 = ($in);
                    $mUcs4 = ($mUcs4 & 0x07) << 18;
                    $mState = 3;
                    $mBytes = 4;
                } else if (0xF8 == (0xFC & ($in))) {
                    /* First octet of 5 octet sequence.
                     *
                     * This is illegal because the encoded codepoint must be either
                     * (a) not the shortest form or
                     * (b) outside the Unicode range of 0-0x10FFFF.
                     * Rather than trying to resynchronize, we will carry on until the end
                     * of the sequence and let the later error handling code catch it.
                     */
                    $mUcs4 = ($in);
                    $mUcs4 = ($mUcs4 & 0x03) << 24;
                    $mState = 4;
                    $mBytes = 5;
                } else if (0xFC == (0xFE & ($in))) {
                    // First octet of 6 octet sequence, see comments for 5 octet sequence.
                    $mUcs4 = ($in);
                    $mUcs4 = ($mUcs4 & 1) << 30;
                    $mState = 5;
                    $mBytes = 6;
                } else {
                    /* Current octet is neither in the US-ASCII range nor a legal first
                     * octet of a multi-octet sequence.
                     */
                    return false;
                }
            } else {
                // When mState is non-zero, we expect a continuation of the multi-octet
                // sequence
                if (0x80 == (0xC0 & ($in))) {
                    // Legal continuation.
                    $shift = ($mState - 1) * 6;
                    $tmp = $in;
                    $tmp = ($tmp & 0x0000003F) << $shift;
                    $mUcs4 |= $tmp;

                    if (0 == --$mState) {
                        /* End of the multi-octet sequence. mUcs4 now contains the final
                         * Unicode codepoint to be output
                         *
                         * Check for illegal sequences and codepoints.
                         */

                        // From Unicode 3.1, non-shortest form is illegal
                        if (((2 == $mBytes) && ($mUcs4 < 0x0080)) ||
                          ((3 == $mBytes) && ($mUcs4 < 0x0800)) ||
                          ((4 == $mBytes) && ($mUcs4 < 0x10000)) ||
                          (4 < $mBytes) ||
                          // From Unicode 3.2, surrogate characters are illegal
                          (($mUcs4 & 0xFFFFF800) == 0xD800) ||
                          // Codepoints outside the Unicode range are illegal
                          ($mUcs4 > 0x10FFFF)) {
                            return false;
                        }
                        if (0xFEFF != $mUcs4) {
                            // BOM is legal but we don't want to output it
                            $out[] = $mUcs4;
                        }
                        //initialize UTF8 cache
                        $mState = 0;
                        $mUcs4  = 0;
                        $mBytes = 1;
                    }
                } else {
                    /* ((0xC0 & (*in) != 0x80) && (mState != 0))
                     *
                     * Incomplete multi-octet sequence.
                     */
                    return false;
                }
            }
        }

        //this bit is mine, to return as U+XXXX...
        $return = '';
        foreach ($out as $num) {
            $return .= 'U+' . str_pad(dechex($num), 4, '0', STR_PAD_LEFT) . ' ';
        }
        $return = strtoupper(rtrim($return));

        return $return;
    }
The following function is derived from https://hsivonen.fi/php-utf8/. It
turns a utf-8 encoded character into its related hex formated codepoint.

@param  string $str  The utf-8 character
@return string       The unicode codepoint(s)