Online PHP editor | output for XTdjA

<?php $score = 64; $firstName = 'Jack'; $lastName = 'Saliv'; $age = 21; $expected = 'FFFEFF404A00610063006B00530061006C00690076FFFEFF15'; $expectedCorrected = 'FFFEFF404A00610063006B00530061006C0069007600FFFEFF15'; // Convert to UTF-16LE and get hex, https://stackoverflow.com/a/16080439/231316 $nameAsUtf16LE = unpack('H*', mb_convert_encoding($firstName.$lastName, 'UTF-16LE', 'UTF-8')); // UTF-16LE BOM $utf16LeBom = 'FFFE'; // Convert to hex strings $scoreAsHex = dechex($score); $ageAsHex = dechex($age); $finalString = sprintf( '%1$s%2$s%3$s', $utf16LeBom.$scoreAsHex, strtoupper($nameAsUtf16LE[1]), // This is 1-based, not 0-based $utf16LeBom.$ageAsHex, ); $numberPadding = 'FF'; $finalStringWithNumbersPadded = sprintf( '%1$s%2$s%3$s', $utf16LeBom.$numberPadding.$scoreAsHex, strtoupper($nameAsUtf16LE[1]), // This is 1-based, not 0-based $utf16LeBom.$numberPadding.$ageAsHex, ); echo 'Calculated : '.$finalString; echo PHP_EOL; echo 'Padded : '.$finalStringWithNumbersPadded; echo PHP_EOL; echo 'Expected : '.$expected; echo PHP_EOL; echo 'Expected Corrected : '.$expectedCorrected; assert($finalStringWithNumbersPadded === $expectedCorrected);