how to check file is there or not if there prints it is ther ,if not create a file

how to check file is there or not if there prints it is ther ,if not create a file
<?php
$filename ='file.txt';	or images/applie.jpg
echo file_exists($filename);	prints 1 if file is there , if fileis not there it prints 0 like a boolean
?>	asssign the file txt to file nam e variable
<?php
$filename ='file.txt';	file.txt assigns to filename variable
if (file_exists($filename){	if file exists means 1, it prints file is exists
echo'file already exists!';	if file is not there
}else{	it create the file
$file = fopen($filename, 'w');	file is created, and write action is going to take
fwrite($file, 'file is now created');	write the data to that file
fclose($file);	close the file
echo 'file is now created and written';	print file is now created and written
}
?> how to check file is there or not if there prints it is ther ,if not create a file file name assigned how to prints boolean values if file is there  file_exists how to check the file is threr or not, if not there how to create how to checkfile is there or not file_exists echo if else fopen how to create a file if it is not there fwrite fclose echo