need help on a piece of code from PHP 5 Social Networking -

i'm trying more advanced php , pick book php 5 social networking michael peacock. while book seemed interesting didn't involved in details of code. function i'm trying figure out is,

    public function geturldata() {     $urldata = ( isset( $_get['page'] ) ) ? $_get['page'] : '' ;      $this->urlpath = $urldata;      if( $urldata == '' )     {         $this->urlbits[] = '';         $this->urlpath = '';     }     else     {         $data = explode( '/', $urldata );          while ( !empty( $data ) && strlen( reset( $data ) ) === 0 )         {             //notes: php array_shift — shift element off beginning of array             array_shift( $data );         }           while ( !empty( $data ) && strlen( end( $data ) ) === 0)         {             array_pop($data);         }          $this->urlbits = $this->array_trim( $data );     } } 

this part of larger class , $_get['page'] this: relationships/mutual/3. main question happening in else section. think happening it's removing empty array indexes question that.

any appreciated.

edit: added array_trim function part of class

    private function array_trim( $array ) {     while ( ! empty( $array ) && strlen( reset( $array ) ) === 0)     {         array_shift( $array );     }      while ( !empty( $array ) && strlen( end( $array ) ) === 0)     {         array_pop( $array );     }      return $array; } 

    public function geturldata() { 

gets 'page', data can obtained $_get url: instance: http://mysite.com/?page=contact

if 'page' has been set, assigned $urldata, else $urldata=''

    $urldata = ( isset( $_get['page'] ) ) ? $_get['page'] : '' ;      $this->urlpath = $urldata;      if( $urldata == '' )     {         $this->urlbits[] = '';         $this->urlpath = '';     }     else     { 

now creating array substrings $urldata splited '/'

        $data = explode( '/', $urldata ); 

if array $data not empty (otherwise accessing non-existent element raise exception) or lenght of first element equal 0, removes first element array.

        while ( !empty( $data ) && strlen( reset( $data ) ) === 0 )         {             //notes: php array_shift — shift element off beginning of array             array_shift( $data );         } 

if array $data not empty (otherwise accessing non-existent element raise exception) or lenght of last element equal 0, removes last element array.

        while ( !empty( $data ) && strlen( end( $data ) ) === 0)         {             array_pop($data);         } 

array_trim custom function, not sure kind of trimming too

        $this->urlbits = $this->array_trim( $data );     } 

}