How can I convert a UTF-8 string to UCS-2 code points in PHP 4 or 5?

Getting UCS-2 Code Points for UTF-8 Strings in PHP 4 or 5

To obtain UCS-2 code points for a UTF-8 string, you can leverage existing utilities available in PHP. Consider using libraries like iconv to facilitate this conversion.

In case you prefer a custom solution, it's crucial to understand the UTF-8 format. Each code point is stored as 1-4 bytes, based on its value. The following ranges apply:

• 1 byte: 0xxxxxxx
• 2 bytes: 110xxxxx 10xxxxxx
• 3 bytes: 1110xxxx 10xxxxxx 10xxxxxx
• 4 bytes: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx

To determine the number of bytes in a character, examine the first byte. A 0 prefix indicates a 1-byte character, 110 indicates 2 bytes, 1110 a 3-byte character, and 11110 a 4-byte character.

Once you know the character's size, you can perform bitwise operations to convert it. Note that UCS-2 cannot represent characters above U FFFF.

For reference, here's a PHP 4 or 5 function that you can use:

<code class="php">function get_ucs2_codepoint($char)
{
    $byte = ord($char);
    if ($byte < 128) {
        return $byte;
    } elseif ($byte < 224) {
        return (($byte & 63) << 6) | (ord($char[1]) & 63);
    } elseif ($byte < 240) {
        return (($byte & 31) << 12) | ((ord($char[1]) & 63) << 6) | (ord($char[2]) & 63);
    } else {
        return 0; // UCS-2 cannot handle code points this high
    }
}</code>

Remember, this function doesn't handle all Unicode characters, only those representable with UCS-2. If you need to handle full Unicode, you should use alternative libraries or PHP 6 functions.

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