What am I doing wrong while trying to find file type (PHP)

Here is my code, I have a file name ($fname) and need to assign $pClass to the file type with a "-" afterwards. Currently I always get text-, no matter what file type it is.

//This gets the extention for the file and assigns the class to the icon <i>
        $pieces = explode('.', $fname);
        $ext = array_pop($pieces);

        if($ext == (('txt')||('rtf')||('log')||('docx'))){
          $pClass = 'text-';
        }
        else if($ext == (('zip')||('sitx')||('7z')||('rar')||('gz'))){
          $pClass = 'archive-';
        }
        else if($ext == (('php')||('css')||('html')||('c')||('cs')||('java')||('js')||('xml')||('htm')||('asp'))){
          $pClass = 'code-';
        }
        else if($ext == (('png')||('bmp')||('dds')||('gif')||('jpg')||('psd')||('pspimage')||('tga')||('svg'))){
          $pClass = 'image-';
        }
        else {
          $pClass = '';
        }