utf8_encode

This function does not attempt to guess the current encoding of the provided string, it assumes it is encoded as ISO-8859-1 (also known as "Latin 1") and converts to UTF-8. Since every sequence of bytes is a valid ISO-8859-1 string, this never results in an error, but will not result in a useful string if a different encoding was intended.

Many web pages marked as using the ISO-8859-1 character encoding actually use the similar Windows-1252 encoding, and web browsers will interpret ISO-8859-1 web pages as Windows-1252. Windows-1252 features additional printable characters, such as the Euro sign (€) and curly quotes (“ ”), instead of certain ISO-8859-1 control characters. This function will not convert such Windows-1252 characters correctly. Use a different function if Windows-1252 conversion is required.

This function is deprecated as of PHP 8.2.0, and will be removed in a future version. Existing uses should be checked and replaced with appropriate alternatives.

Similar functionality can be achieved with mb_convert_encoding(), which supports ISO-8859-1 and many other character encodings.

<?php
$iso8859_1_string = "\xEB"; // 'ë' (e with diaeresis) in ISO-8859-1
$utf8_string = mb_convert_encoding($iso8859_1_string, 'UTF-8', 'ISO-8859-1');
echo bin2hex($utf8_string), "\n";

$iso8859_7_string = "\xEB"; // the same string in ISO-8859-7 represents 'λ' (Greek lower-case lambda)
$utf8_string = mb_convert_encoding($iso8859_7_string, 'UTF-8', 'ISO-8859-7');
echo bin2hex($utf8_string), "\n";

$windows_1252_string = "\x80"; // '€' (Euro sign) in Windows-1252, but not in ISO-8859-1
$utf8_string = mb_convert_encoding($windows_1252_string, 'UTF-8', 'Windows-1252');
echo bin2hex($utf8_string), "\n";
?>

The above example will output:

c3ab
cebb
e282ac

Other options which may be available depending on the extensions installed are UConverter::transcode and iconv().

The following all give the same result:

<?php
$iso8859_1_string = "\x5A\x6F\xEB"; // 'Zoë' in ISO-8859-1

$utf8_string = utf8_encode($iso8859_1_string);
echo bin2hex($utf8_string), "\n";

$utf8_string = mb_convert_encoding($iso8859_1_string, 'UTF-8', 'ISO-8859-1');
echo bin2hex($utf8_string), "\n";

$utf8_string = UConverter::transcode($iso8859_1_string, 'UTF8', 'ISO-8859-1');
echo bin2hex($utf8_string), "\n";

$utf8_string = iconv('ISO-8859-1', 'UTF-8', $iso8859_1_string);
echo bin2hex($utf8_string), "\n";
?>

The above example will output:

5a6fc3ab
5a6fc3ab
5a6fc3ab
5a6fc3ab