Online PHP editor | output for t6HIV

<?php function utf8_scrub($str, $substitute = "\xE3\x80\x93") { $regex = '/ ([\x00-\x7F] # U+0000 - U+007F |[\xC2-\xDF][\x80-\xBF] # U+0080 - U+07FF | \xE0[\xA0-\xBF][\x80-\xBF] # U+0800 - U+0FFF |[\xE1-\xEC\xEE\xEF][\x80-\xBF]{2} # U+1000 - U+CFFF | \xED[\x80-\x9F][\x80-\xBF] # U+D000 - U+D7FF | \xF0[\x90-\xBF][\x80-\xBF]{2} # U+10000 - U+3FFFF |[\xF1-\xF3][\x80-\xBF]{3} # U+40000 - U+FFFFF | \xF4[\x80-\x8F][\x80-\xBF]{2}) # U+100000 - U+10FFFF |(\xE0[\xA0-\xBF] # U+0800 - U+0FFF (invalid) |[\xE1-\xEC\xEE\xEF][\x80-\xBF] # U+1000 - U+CFFF (invalid) | \xED[\x80-\x9F] # U+D000 - U+D7FF (invalid) | \xF0[\x90-\xBF][\x80-\xBF]? # U+10000 - U+3FFFF (invalid) |[\xF1-\xF3][\x80-\xBF]{1,2} # U+40000 - U+FFFFF (invalid) | \xF4[\x80-\x8F][\x80-\xBF]?) # U+100000 - U+10FFFF (invalid) |(.) # invalid 1-byte /xs'; // $matches[1]: valid character // $matches[2]: invalid 3-byte or 4-byte character // $matches[3]: invalid 1-byte $ret = preg_replace_callback( $regex, function ($matches) use ($substitute) { if (isset($matches[2]) || isset($matches[3])) { return $substitute; } return $matches[1]; }, $str ); return $ret; } $examples = array( 'Valid ASCII' => "a", 'Valid 2 Octet Sequence' => "\xc3\xb1", 'Invalid 2 Octet Sequence' => "\xc3\x28", 'Invalid Sequence Identifier' => "\xa0\xa1", 'Valid 3 Octet Sequence' => "\xe2\x82\xa1", 'Invalid 3 Octet Sequence (in 2nd Octet)' => "\xe2\x28\xa1", 'Invalid 3 Octet Sequence (in 3rd Octet)' => "\xe2\x82\x28", 'Valid 4 Octet Sequence' => "\xf0\x90\x8c\xbc", 'Invalid 4 Octet Sequence (in 2nd Octet)' => "\xf0\x28\x8c\xbc", 'Invalid 4 Octet Sequence (in 3rd Octet)' => "\xf0\x90\x28\xbc", 'Invalid 4 Octet Sequence (in 4th Octet)' => "\xf0\x28\x8c\x28", 'Valid 5 Octet Sequence (but not Unicode!)' => "\xf8\xa1\xa1\xa1\xa1", 'Valid 6 Octet Sequence (but not Unicode!)' => "\xfc\xa1\xa1\xa1\xa1\xa1", ); foreach ($examples as $k => $v) { echo "{$k}\n"; echo utf8_scrub($v); echo "\n"; }