PHP Decode

<?php session_start();include(base64_decode('Y29uZmlnL2NvbmYucGhw'));if(isset($_SESSION[base64_decode('bG9nZ2Vk')])&&$_SESSION[base64_decode('bG9nZ2Vk')]===base64_decode('dHJ1ZQ==')){header(base64_decode('TG9jYXRpb246IGluZGV4LnBocA=='));exit();}else{$d0=$b1->b2(base64_decode('U0VMRUNUIHJlYWR5IEZST00gaW5mb3M='));$d0->d3();$z4=$d0->f5();if($z4[base64_decode('cmVhZHk=')]===base64_decode('MQ==')){header(base64_decode('TG9jYXRpb246IGluZGV4LnBocA=='));$v6=base64_decode('b2theSBJJ20gY29vbCwgSSBnaXZlIHlvdSB0aGUga2V5IGZvciBlbnRlciBpbiB0aGUgdGhlIDR0aCByYXAgY29udGVuZGVycyA6IGJyYWluc2hlbGw=');}}if(!isset($_GET[base64_decode('YWN0aW9u')])){header(base64_decode('TG9jYXRpb246IGhlbGxvLnBocD9hY3Rpb249Y29uZmlndXJl'));exit();}if(isset($_GET[base64_decode('YWN0aW9u')])){$d7=htmlspecialchars($_GET[base64_decode('YWN0aW9u')]);if($d7===base64_decode('cmVnaXN0ZXI=')){include(base64_decode('aW5jbHVkZS9yZWdpc3Rlci5waHA='));if(isset($_POST[base64_decode('dXNlcm5hbWU=')])){$n8=(isset($_POST[base64_decode('dXNlcm5hbWU=')])&&trim($_POST[base64_decode('dXNlcm5hbWU=')])!='')?htmlspecialchars($_POST[base64_decode('dXNlcm5hbWU=')]):null;$i9=(isset($_POST[base64_decode('cGFzc3dvcmQ=')])&&trim($_POST[base64_decode('cGFzc3dvcmQ=')])!='')?htmlspecialchars($_POST[base64_decode('cGFzc3dvcmQ=')]):null;if(isset($n8,$i9)){$d0=$b1->b2(base64_decode('SU5TRVJUIGludG8gdXNlcmluZm8gKHVzZXJuYW1lLCBwYXNzd29yZCkgVkFMVUVTICg6dXNlcm5hbWUsIDpwYXNzd29yZCk='));$d0->ja(base64_decode('OnVzZXJuYW1l'),$n8,PDO::PARAM_STR);$d0->ja(base64_decode('OnBhc3N3b3Jk'),md5(sha1($i9)),PDO::PARAM_STR);$d0->d3();$_SESSION[base64_decode('bG9nZ2Vk')]=base64_decode('dHJ1ZQ==');header(base64_decode('TG9jYXRpb246IGluZGV4LnBocA=='));}}}elseif($d7===base64_decode('Y29uZmlndXJl')){include(base64_decode('aW5jbHVkZS9jb25maWd1cmUucGhw'));if(isset($_POST[base64_decode('c3FscGF0aA==')])){$pb=base64_decode('TVJSREdNSldIQTJXQ09MR0c1UldFTVk9');$rc=htmlspecialchars($_POST[base64_decode('c3FscGF0aA==')]);if(isset($_POST[base64_decode('cHlwYXRo')])&$_POST[base64_decode('cHlwYXRo')]!=''){echo base64_decode('cHlwYXRoIDog').$_POST[base64_decode('cHlwYXRo')];$kd=htmlspecialchars($_POST[base64_decode('cHlwYXRo')]);$d0=$b1->b2(base64_decode('SU5TRVJUIGludG8gaW5mb3MgKHNxbHBhdGgsIG9zLCByZWFkeSwgcHJlc2V0LCBweXBhdGgpIFZBTFVFUyAoOnNxbHBhdGgsIDEsIDEsIDAsIDpweXBhdGgp'));$d0->ja(base64_decode('OnNxbHBhdGg='),$rc,PDO::PARAM_STR);$d0->ja(base64_decode('OnB5cGF0aA=='),$kd,PDO::PARAM_STR);$d0->d3();header(base64_decode('TG9jYXRpb246IGhlbGxvLnBocD9hY3Rpb249cmVnaXN0ZXI='));}else{$xe=0;$d0=$b1->b2(base64_decode('SU5TRVJUIGludG8gaW5mb3MgKHNxbHBhdGgsIG9zLCByZWFkeSwgcHJlc2V0LCBweXBhdGgpIFZBTFVFUyAoOnNxbHBhdGgsIDAsIDEsIDAsICcnKQ=='));$d0->ja(base64_decode('OnNxbHBhdGg='),$rc,PDO::PARAM_STR);$d0->d3();$lf=base64_decode('TUU0VEFNQlhHVTJXTVlKVUdSVEdJT0JYSEEyV0NZM0JIQTJXSU1BPQ==');header(base64_decode('TG9jYXRpb246IGhlbGxvLnBocD9hY3Rpb249cmVnaXN0ZXI='));}}}}?>