文件存在于PHP中，带有日文字符

I have a file in あ.gif under images folder. Now I want to check file exist or not but the japanese character was not accepting and it return output as false, But there is a file in あ.gif

Here is my code...

$path    = $WRITING_IMG_PATH;
$file    = "あ.gif";
$fullfilename =$path.$file;
if (file_exists($file)) {
    echo $file;
} else {
    echo "No file";
}

In my code it returns false, if there is file in that images folder.