The **`touch()`** function in PHP is used to set the access and modification time of a specified file. The file name and access and modification times are sent as parameters. If the `atime` or `time` parameter is not provided, default system time is used instead.

# Syntax

```Perl
touch(string $filename, int $time = time(), int $atime = ?): bool
```

# Parameter

* **`filename`**: The name of the file being touched.

* **`time`**: The touch time. If `time` is not supplied, the current system time is used. 
* **`atime`**: If present, the access time of the given file name is set to the value of `atime`. Otherwise, it is set to the value passed to the `time` parameter. If neither is present, the current system time is used.

# Return value

`touch()` returns `true` on success and `false` on failure.

# Code
The code below shows how the `touch()` function may be used. We provide the `filename` as `temp.txt` for the temporary text file. 

Next, we use the `time()` function to get the current time, store it as `access_time`, and wait for $2$ seconds, after which we make another call to `time()` and store the new time in the `mod_time` variable.

In the `if` condition, we call `touch()` with the `access_time`, `mod_time`, and `filename` parameters. If the operation succeeds, we print `atime` and `mtime`, which can be obtained using the `stat()` method, which provides stats for the particular file given in the argument.

<?php 
$filename = "temp.txt";
$access_time = time();
sleep(2);
$mod_time = time();
if (touch($filename, $access_time, $mod_time)) {
    print_r( $filename." mod time and atime set!\n");
    print_r('mtime: '.stat($filename)['mtime']."\n");
    print_r('atime: '.stat($filename)['atime']."\n");    
} else {
    print_r("modification time of ".$filename." could not be changed\n");
}

?>

What is the touch() function in PHP?

Sets a file's access and modification times with optional parameters. Returns true on success, false on failure.