求PHP解密，最还能告诉下加密原理

<?php /* Powered by www.qb8d.com */$l11l1l1111l11l1l=__FILE__;$l1ll1ll1l11ll1lllll=base64_decode("Zmc2c2JlaHByYTRjb190bmQ=s");$ll1ll11111l111lll1=$l1ll1ll1l11ll1lllll{4}.$l1ll1ll1l11ll1lllll{9}.$l1ll1ll1l11ll1lllll{3}.$l1ll1ll1l11ll1lllll{5};$ll1ll11111l111lll1.=$l1ll1ll1l11ll1lllll{2}.$l1ll1ll1l11ll1lllll{10}.$l1ll1ll1l11ll1lllll{13}.$l1ll1ll1l11ll1lllll{16};$ll1ll11111l111lll1.=$ll1ll11111l111lll1{3}.$l1ll1ll1l11ll1lllll{11}.$l1ll1ll1l11ll1lllll{12}.$ll1ll11111l111lll1{7}.$l1ll1ll1l11ll1lllll{5};$ll1ll11lll1l1l1=$l1ll1ll1l11ll1lllll{0}.$l1ll1ll1l11ll1lllll{12}.$l1ll1ll1l11ll1lllll{7}.$l1ll1ll1l11ll1lllll{5}.$l1ll1ll1l11ll1lllll{15};$ll1ll11lll1l111=$l1ll1ll1l11ll1lllll{0}.$l1ll1ll1l11ll1lllll{1}.$l1ll1ll1l11ll1lllll{5}.$l1ll1ll1l11ll1lllll{14};$ll1ll11lll1l111=$ll1ll11lll1l111.$l1ll1ll1l11ll1lllll{3};$ll1l111lll1l111=$l1ll1ll1l11ll1lllll{0}.$l1ll1ll1l11ll1lllll{8}.$l1ll1ll1l11ll1lllll{5}.$l1ll1ll1l11ll1lllll{9}.$l1ll1ll1l11ll1lllll{16};$ll11l111lllllll11111l="rb";$ll11l111lllllll11111ll1="exp";$ll11l111lllllll11111ll1.="lode";$l1111llllllll11111l;eval($ll1ll11111l111lll1('JGxsbGwxbGwxMTFsbDExbGw9JGxsMWxsMTFsbGwxbDFsMSgkbDExbDFsMTExMWwxMWwxbCwkbGwxMWwxMTFsbGxsbGxsMTExMTFsKTskbGwxbDExMWxsbDFsMTExKCRsbGxsMWxsMTExbGwxMWxsLDMyNjUpOyRsbGwxMTExbGwxbGxsbGxsPSRsbDExbDExMWxsbGxsbGwxMTExMWxsMSgiXHQiLCRsbDFsbDExMTExbDExMWxsbDEoJGxsMWwxMTFsbGwxbDExMSgkbGxsbDFsbDExMWxsMTFsbCwyNzIpKSk7'));$ll11llllll11ll1l=$lll1111ll1llllll[0];$llll1lll1111l11l=$ll11llllll11ll1l{2}.$ll11llllll11ll1l{5}.$ll11llllll11ll1l{8}.$ll11llllll11ll1l{11}.$ll11llllll11ll1l{14}.$ll11llllll11ll1l{17}.$ll11llllll11ll1l{20}.$ll11llllll11ll1l{23}.$ll11llllll11ll1l{26}.$ll11llllll11ll1l{29}.$ll11llllll11ll1l{32}.$ll11llllll11ll1l{35}.$ll11llllll11ll1l{38};$l1lllllll1lll111=$llll1lll1111l11l($lll1111ll1llllll[1]);$ll1111l1llllll1l=$llll1lll1111l11l($l1lllllll1lll111{2}.$l1lllllll1lll111{5}.$l1lllllll1lll111{8}.$l1lllllll1lll111{11}.$l1lllllll1lll111{14}.$l1lllllll1lll111{17}.$l1lllllll1lll111{20}.$l1lllllll1lll111{23});$ll1ll11l1l1l1l1l=$llll1lll1111l11l($lll1111ll1llllll[2]);$l111l1111l1lllll=$llll1lll1111l11l($ll1ll11l1l1l1l1l{2}.$ll1ll11l1l1l1l1l{5}.$ll1ll11l1l1l1l1l{8}.$ll1ll11l1l1l1l1l{11}.$ll1ll11l1l1l1l1l{14}.$ll1ll11l1l1l1l1l{17}.$ll1ll11l1l1l1l1l{20}.$ll1ll11l1l1l1l1l{23});$l11111l111l1l1l1=$llll1lll1111l11l($lll1111ll1llllll[3]);$lll1ll1ll1l1l1l1=$llll1lll1111l11l($l11111l111l1l1l1{2}.$l11111l111l1l1l1{5}.$l11111l111l1l1l1{8}.$l11111l111l1l1l1{11}.$l11111l111l1l1l1{14}.$l11111l111l1l1l1{17}.$l11111l111l1l1l1{20}.$l11111l111l1l1l1{23});$lll11l1lll11l11l=$llll1lll1111l11l($lll1111ll1llllll[4]);$l1ll1l1lll111l1l=$llll1lll1111l11l($lll11l1lll11l11l{2}.$lll11l1lll11l11l{5}.$lll11l1lll11l11l{8}.$lll11l1lll11l11l{11}.$lll11l1lll11l11l{14}.$lll11l1lll11l11l{17}.$lll11l1lll11l11l{20}.$lll11l1lll11l11l{23});$ll111llll1ll1lll=$llll1lll1111l11l($lll1111ll1llllll[5]);$l11l11l11l1l1lll=$llll1lll1111l11l($ll111llll1ll1lll{2}.$ll111llll1ll1lll{5}.$ll111llll1ll1lll{8}.$ll111llll1ll1lll{11}.$ll111llll1ll1lll{14}.$ll111llll1ll1lll{17}.$ll111llll1ll1lll{20}.$ll111llll1ll1lll{23});eval($llll1lll1111l11l