Description:
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In the source code, $this->filepath is overwritten unexpectly in the assignment 
$this->$tempFilepath=$this->$filepath.".tmp";

Reproduce code:
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class Zone{

        var $path; // The path to store zone files
        var $filepath; // The zone file with absolute filepath
        var $tempFilepath; // Temporary file
        var $domain; // Domain object

        function Zone($domainTemp,$pathTemp){
                if(preg_match("/^\//",$pathTemp)){
                        $this->$path=$pathTemp;
                        $this->$domain=new Domain($domainTemp.".");
                        $this->$filepath=$pathTemp."/".$domainTemp.".zone";
                        print $this->$filepath;
                        $this->$tempFilepath=$this->$filepath.".tmp";
                        print $this->$filepath;
...
...

Expected result:
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I create the object 
$zone=new Zone("mydomain.com","/var/named");

$this->$filepath should be /var/named.mydomain.com.zone
$this->$tempFilepath should be /var/named.mydomain.com.zone.tmp



Actual result:
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both variable metioned above have the same value /var/named.mydomain.com.zone.tmp