Fixed

It could be that whoever did the PHP translation may have accidentally transposed the expected/actual arguments in the test cases.

PHP Sample Tests seem to be broken - expected values are missing some letters.

Example:

Failed asserting that two strings are equal.
Expected: 'codeas'
Actual  : 'codewars'

While sample tests are written as:

$this->assertEquals($c->encode('codewars'), 'rovwsoiv');
$this->assertEquals($c->decode('rovwsoiv'), 'codewars');