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How to convert text to unicode code point like \u0054\u0068\u0069\u0073 using php?

I’m trying to convert all characters that can’t fit into a 7-bit ANSI character into an escaped form, \uN, where N is its decimal value. Here’s what I’ve come up with:

private static function escape($str) {
    return preg_replace_callback('~[\\x{007F}-\\x{FFFF}]~u',function($m){return '\\u'.ord($m[0]);},$str);
}

I’ve tried it with characters like Gamma,

echo self::escape('Γ');

But I get \u206 back out instead of \u915. I can’t figure out where I’m going wrong… ideas?

Actually, it appears that either the ord() function doesn’t give me the value or I want, or maybe the encoding on my .php file is wrong?

Answer 1

I had to refresh my memory on exactly how UTF-8 works, but here is a utf8_ord() function, and a complementing utf8_chr(). The chr() is lifted pretty much verbatim from my answer here.

function utf8_ord ($chr)
{
    $bytes = array_values(unpack('C*', $chr));

    switch (count($bytes)) {
        case 1:
            return $bytes[0] < 0x80
                ? $bytes[0]
                : false;
        case 2:
            return ($bytes[0] & 0xE0) === 0xC0 && ($bytes[1] & 0xC0) === 0x80
                ? (($bytes[0] & 0x1F) << 6) | ($bytes[1] & 0x3F)
                : false;
        case 3:
            return ($bytes[0] & 0xF0) === 0xE0 && ($bytes[1] & 0xC0) === 0x80 && ($bytes[2] & 0xC0) === 0x80 
                ? (($bytes[0] & 0x0F) << 12) | (($bytes[1] & 0x3F) << 6) | ($bytes[2] & 0x3F)
                : false;
        case 4:
            return ($bytes[0] & 0xF8) === 0xF0 && ($bytes[1] & 0xC0) === 0x80 && ($bytes[2] & 0xC0) === 0x80 && ($bytes[3] & 0xC0) === 0x80
                ? (($bytes[0] & 0x07) << 18) | (($bytes[1] & 0x3F) << 12) | (($bytes[2] & 0x3F) << 6) | ($bytes[3] & 0x3F)
                : false;
    }

    return false;
}

function utf8_chr ($ord)
{
    switch (true) {
        case $ord < 0x80:
            return pack('C*', $ord & 0x7F);
        case $ord < 0x0800:
            return pack('C*', (($ord & 0x07C0) >> 6) | 0xC0, ($ord & 0x3F) | 0x80);
        case $ord < 0x010000:
            return pack('C*', (($ord & 0xF000) >> 12) | 0xE0, (($ord & 0x0FC0) >> 6) | 0x80, ($ord & 0x3F) | 0x80);
        case $ord < 0x110000:
            return pack('C*', (($ord & 0x1C0000) >> 18) | 0xF0, (($ord & 0x03F000) >> 12) | 0x80, (($ord & 0x0FC0) >> 6) | 0x80, ($ord & 0x3F) | 0x80);
    }

    return false;
}