mb_string Encoding Error

Why This Happens

PHP's mb_string functions can attempt to auto-detect encoding, but this is unreliable. When detection fails, the function may return false or produce garbled output. Always specify both source and target encodings explicitly for reliable results.

The Problem

$utf8 = mb_convert_encoding($data, 'UTF-8'); // Source encoding not specified

The Fix

$utf8 = mb_convert_encoding($data, 'UTF-8', 'ISO-8859-1');
// Or detect first with a strict list:
$encoding = mb_detect_encoding($data, ['UTF-8', 'ISO-8859-1', 'ASCII'], true);
if ($encoding === false) {
    throw new RuntimeException('Unable to detect encoding');
}
$utf8 = mb_convert_encoding($data, 'UTF-8', $encoding);

Step-by-Step Fix

1. 1

   Determine the source encoding

   Find out what encoding the source data uses. Check the database charset, file encoding, or API response headers.

2. 2

   Specify encoding explicitly

   Always pass the source encoding as the third parameter to mb_convert_encoding instead of relying on auto-detection.

3. 3

   Validate after conversion

   Use mb_check_encoding() to verify the converted string is valid in the target encoding.