How to Decode Unicode Escape Sequences in PHP?

Decoding Unicode Escape Sequences in PHP

Character encoding can be a confusing topic, especially when working with Unicode escape sequences like "u00ed". If you're wondering how to decode these sequences into proper UTF-8 characters in PHP, this article will provide a straightforward solution.

Using preg_replace_callback

To decode Unicode escape sequences in PHP, you can use the preg_replace_callback() function. Here's a code snippet that demonstrates its usage:

$str = preg_replace_callback('/\\u([0-9a-fA-F]{4})/', function ($match) {
    return mb_convert_encoding(pack('H*', $match[1]), 'UTF-8', 'UCS-2BE');
}, $str);

This regular expression pattern matches all Unicode escape sequences and uses a callback function to decode each match. The callback function does the following:

• Converts the hex representation of the Unicode code point (e.g., "00ed") into a binary string using pack('H*').
• Decodes the binary string into UTF-8 using mb_convert_encoding().

Handling Different Unicode Encodings

If your Unicode data is based on UTF-16 instead of UCS-2, which is common in C/C , Java, and JSON, you can use a slightly different version of the callback function:

$str = preg_replace_callback('/\\u([0-9a-fA-F]{4})/', function ($match) {
    return mb_convert_encoding(pack('H*', $match[1]), 'UTF-8', 'UTF-16BE');
}, $str);

This change ensures that the decoding function correctly handles UTF-16 encoded data.

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