deleting and renaming files with php

<?php
$filename = 'mango.jpg';	assigned the name of the file
if (@unlink($filename)){	deleted the file , if file deleted yes
echo 'file <strong>' .$filename.' </strong>has beenn deleted;	print file is deleted
} else {	if not
if (@file_exists ($filename)){	checks file is there or not if file is ther prints 1
echo 'file <strong.' .$filename. '</strong> exists but cannot be deleted!'	file is there
} else {
echo 'file <strong> '.$filename.' </strong> does not exist!';	if file is not there, does not exists
}
}
?>
rename the file name
<?php
$filename = 'orange.jpg';	assigned orange.jpg to filename
$randno = rand(5555, 9999);	some random number generated between these two
$newname = $randno.'.jpg';	assigned that name to newname
if (@rename ($filename, $newname)){	change the name of the file from rightside
echo 'file <strong>'. $filename. '</strong> has been renamed to <strong>'. $newname.' </strong>';	file renamed , it prints file is renamed , if not file not remand
} else{
echo 'failed';	if u again open this file.php, it shows failed because it is alreadt rename the file of that orange.jpog
}
?>

how to delete the file
how to delete the file	unlink
how to check file is deleted or not	file_exists
how to rename the file name with any random number	rand(larger, smaller)
	rename
	if else