ZipArchive corrupting files

[NightMonkey]

Hi,

I am trying to rename all of the files in a zip archive by adding a prefix to their names. This is working fine however when I try and extract the files from the finished archive it says they are corrupt. Here is the code im using:

$zip = new ZipArchive();
    if ($zip->open($targetpath,ZIPARCHIVE::OVERWRITE)===true)
    {  
         // prefix all of the files with the clients name
         for($i = 0; $i < $zip->numFiles; $i++)
         {  
             $zip->renameIndex($i,$client.'-'.$zip->getNameIndex($i));
         }
         if (!$zip->close()) echo 'Failed to rename files';
     }

Does anyone know why this is corrupting the archive?