too long

I'm writing a PHP class and am having considerable trouble defining scope. I've read a lot of articles around this concept on SO, but I can't seem to determine what is the matter with my code.

class Logger {

    private static $logger ;
    private $res ;
    private $file ;
    private $mode ;

public static function getInstance() {
    if (!self::$logger) $instance = new self() ;
    self::$logger = $instance ;
    return self::$logger ;
}

private function initializeLogger( ) {

    $this->file = '/tmp/mydirectory/mylog.log' ;
    $this->res =  fopen($this->file, 'a') or exit("Can't open ".$this->file);
}


public function write( $message , $modeLevel ) {

    if ( !is_resource($this->res )) {
        $this->initializeLogger( ) ;
    }

    fwrite($this->res, "$message" . PHP_EOL);

}

public function close()
{
    fclose(self::$logger);
}
}


$log = Logger::getInstance();
$log.write( "WOW, it's working!!" , 1 );

This code, when run produces: Call to undefined function write() in /var/www/myfile.php

Any advice on how to create an object which can be referenced in a non static way but is

Replace:

$log.write( "WOW, it's working!!" , 1 );

with:

$log->write( "WOW, it's working!!" , 1 );

$log is an instance of the class Logger, and write is a method of this class.

Documentation: PHP classes and objects