Why Are Some Unicode Characters in JSON Encoded as Escape Sequences?

JSON Weird Special Unicode Characters Decoding: An Explanation

In the realm of JSON encoding, "special" Unicode characters can sometimes appear oddly encoded. This article aims to clarify this common issue and explore the underlying reasons.

Why does this phenomenon occur?

The JSON standard allows for special characters to be encoded in multiple ways, including hexadecimal escape sequences. When using json_encode to encode Unicode characters, it often opts for these escape sequences. For instance, the Chinese character "馬" will come out as "u99ac" in the encoded JSON.

This behavior is not an error; rather, it follows the JSON syntax outlined in the ECMAScript standard. In Javascript, string literals can be written using hexadecimal escape sequences to represent any character, including those from the UTF-16 surrogate pair.

Using the Unicode code point, any character can be encoded as "u...". This notation is completely equivalent to the literal character itself, as both will be interpreted as the same entity by a JSON parser.

However, one can configure json_encode to prefer literal character encoding by setting the JSON_UNESCAPED_UNICODE flag when encoding. This will make the result more human-readable but does not alter the underlying meaning of the data.

In conclusion, the seemingly "weird" encoding of Unicode characters in JSON using json_encode is not a matter of incorrect encodings. It is a perfectly valid method that complies with JSON standards. If desired, literal character encoding can be enabled using the JSON_UNESCAPED_UNICODE flag.

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