String Byte conversion for PHP

Let’s look up hex2bin function in php manual.
hex2bin

It says “Decodes hexadecimally encoded binary string”.

Example 1

mb_internal_encoding('UTF-8');
$char = 'あ';

echo bin2hex($char);

result: e38182

This is the unicode standard manual
Unicode.org
UTF8 has 1byte to 4 byte characters.

What happen about in the case of Emoji?
🌸 Cherry blossom: 1F338

mb_internal_encoding('UTF-8');
$char = '🌸';

echo bin2hex($char);

f09f8cb8
A number different from unicode was displayed.
Comversion seems to be done without problems.