If you want to unzip an password protected file with php..try the following command....it works in Unix/Apache environment...I haven't tested in any other environment...

system("`which unzip` -P Password $zipfile -d $des",$ret_val)

Where $zipfile is the path to the .zip to be unzipped and $des is path to the destination directory.....here both absolute and relative path to the script (which contains this system command) will work...

if everything runs well...file should be unzipped at the $des directory..and you will get 0 value for $ret_val , which means success(info-zip.org)

Regards
Krishnendu