public function hasGlobalColorTable()
    {
        $byte = substr($this->logicalScreenDescriptor, 4, 1);
        
        if (strlen($byte) == 1) {
            $byte = unpack('C', $byte)[1];
            $bit = $byte & bindec('10000000');
        }

        return isset($bit) ? (bool) $bit : false;
    }
public function hasGlobalColorTable()
    {
        $byte = substr($this->logicalScreenDescriptor, 4, 1);
        
        if (strlen($byte) == 1) {
            $byte = unpack('C', $byte)[1];
            $bit = $byte & bindec('10000000');
        }

        return isset($bit) ? (bool) $bit : false;
    }
public function hasGlobalColorTable ( ) { $ byte = substr ( $ this -> logicalScreenDescriptor , 4 , 1 ) ; if ( strlen ( $ byte ) == 1 ) { $ byte = unpack ( 'C' , $ byte ) [ 1 ] ; $ bit = $ byte & bindec ( '10000000' ) ; } return isset ( $ bit ) ? ( bool ) $ bit : false ; }
Determines if image has global color table

@return boolean
Determines if image has global color table