iconv UTF-8//IGNORE still produces “illegal character” error

Question

$string = iconv("UTF-8", "UTF-8//IGNORE", $string);

I thought this code would remove invalid UTF-8 characters, but it produces [E_NOTICE] "iconv(): Detected an illegal character in input string". What am I missing, how do I properly strip a string from illegal characters?

Answer 1

The output character set (the second parameter) should be different from the input character set (first param). If they are the same, then if there are illegal UTF-8 characters in the string, iconv will reject them as being illegal according to the input character set.

Answer 2

I know 2 methods how to fix UTF-8 string containing illegal characters:

1. Illegal characters will be replaced by question marks ("?"):

$message = mb_convert_encoding($message, 'UTF-8', 'UTF-8');

2. Illegal characters will be removedL

$message = iconv('UTF-8', 'UTF-8//IGNORE', $message);

The second method actually was described in question. But it doesn't produce any E_NOTICE in my case. I tested with different corrupted UTF-8 strings with error_reporting(E_ALL); and always result was as expected. Possible something was changed since 2012. I tested on PHP 7.2.9 Win.

Answer 3

To simply ignore notice, you can use "@":

$string = @iconv("UTF-8", "UTF-8//IGNORE", $string);