UConverter::transcode

(PHP 5 >= 5.5.0, PHP 7, PHP 8, PECL >= 3.0.0a1)

UConverter::transcode — Convert a string from one character encoding to another

Description

public static UConverter::transcode(
    string $str,
    string $toEncoding,
    string $fromEncoding,
    ?array $options = null
): string|false

Converts str from fromEncoding to toEncoding.

Parameters

str

The string to be converted.

toEncoding

The desired encoding of the result.

fromEncoding

The current encoding used to interpret str.

options

An optional array, which may contain the following keys:

  • 'to_subst' - the substitution character to use in place of any character of str which cannot be encoded in toEncoding. If specified, it must represent a single character in the target encoding.

Return Values

Returns the converted string or false on failure.

Examples

Example #1 Converting from UTF-8 to UTF-16 and back

<?php
$utf8_string = "\x5A\x6F\xC3\xAB"; // 'Zoë' in UTF-8
$utf16_string = UConverter::transcode($utf8_string, 'UTF-16BE', 'UTF-8');
echo bin2hex($utf16_string), "\n";

$new_utf8_string = UConverter::transcode($utf16_string, 'UTF-8', 'UTF-16BE');
echo bin2hex($new_utf8_string), "\n";
?>

The above example will output:

005a006f00eb
5a6fc3ab

Example #2 Invalid characters in input

If the input string contains a sequence of bytes which is not valid in the encoding specified by fromEncoding, they are replaced by Unicode code point U+FFFD (Replacement Character) before converting to toEncoding.

<?php
$invalid_utf8_string = "\xC3"; // incomplete multi-byte UTF-8 sequence
$utf16_string = UConverter::transcode($invalid_utf8_string, 'UTF-16BE', 'UTF-8');
echo bin2hex($utf16_string), "\n";
?>

The above example will output:

fffd

Example #3 Characters which cannot be encoded

If the input string contains characters which cannot be represented in toEncoding, they are replaced with a single character. The default character to use depends on the encoding, and can be controlled using the 'to_subst' option.

<?php
$utf8_string = "\xE2\x82\xAC"; // € (Euro Sign) does not exist in ISO 8859-1

// Default replacement in ISO 8859-1 is "\x1A" (Substitute)
$iso8859_1_string = UConverter::transcode($utf8_string, 'ISO-8859-1', 'UTF-8');
echo bin2hex($iso8859_1_string), "\n";

// Specify a replacement of '?' ("\x3F") instead
$iso8859_1_string = UConverter::transcode(
$utf8_string, 'ISO-8859-1', 'UTF-8', ['to_subst' => '?']
);
echo bin2hex($iso8859_1_string), "\n";

// Since ISO 8859-1 cannot map U+FFFD, invalid input is also replaced by to_subst
$invalid_utf8_string = "\xC3"; // incomplete multi-byte UTF-8 sequence
$iso8859_1_string = UConverter::transcode(
$invalid_utf8_string, 'ISO-8859-1', 'UTF-8', ['to_subst' => '?']
);
echo bin2hex($iso8859_1_string), "\n";
?>

The above example will output:

1a
3f
3f

See Also

  • mb_convert_encoding() - Convert a string from one character encoding to another
  • iconv() - Convert a string from one character encoding to another