PHP:How can I send the Data entered by a user in a text field to a txt file?

In PHP How can I send the D开发者_运维知识库ata entered by a user in a text field to a txt file inside of a folder on my server.

To clear the file and open for writing:

$h = fopen("path and filename", "wb+");

or appending:

$h = fopen("path and filename", "ab+");

To write to the file:

fwrite($h, $myString);

Then close it:

fclose($h);