Why Does json_encode Return an Empty String, and How Can I Fix It?

Understanding the Enigma of json_encode Returning an Empty String

PHP's json_encode function serves to convert an array, object, or scalar value into a JSON string representation. However, in some cases, users encounter the frustrating issue of json_encode returning an empty string instead of the expected output. To unravel this perplexing behavior, let's delve into a reported scenario.

The user attempted to convert a complex PHP structure containing nested arrays into JSON. While a similar structure had been successfully converted in a different script, json_encode failed to perform its intended task in this instance. After some investigative efforts, it became apparent that the encoding was causing the problem.

When the encoding was detected as ASCII using mb_detect_encoding, json_encode functioned as expected. Surprisingly, when the encoding was determined to be UTF8, it ceased to work. A closer examination with json_last_error() revealed an error code indicating malformed UTF-8 characters.

After hours of diligent debugging, the solution was found lying in an encoding issue. Although mb_detect_encoding might have returned inaccurate results, suggesting some strings were not in UTF-8 format, employing utf8_encode() on those strings resolved the problem.

To ensure consistent conversions, a recursive function named utf8ize was introduced. This function iteratively examines an array, converting all contained strings to UTF-8. By invoking this function before using json_encode, the user eliminated the encoding hurdle.

Note: It's worth mentioning that utf8_encode() specifically converts ISO-8859-1 strings to UTF-8. If the input encoding is uncertain or complex, consider alternatives like iconv() or mb_convert_encoding().

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