How can I get a PHP value from an HTML form?
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I have an HTML form as follows:

    <form enctype="multipart/form-data" action=" " method="post">
    <input name="username" type="text"/>
    <input type="submit" value="Upload" class="btn btn-primary"/><br/>
    </form>

and I want that the user of this form enters data in the input box. Then I would like this data to be the value of a PHP string - e.g. $username = "MY_NAME"; where MY_NAME is the value of the HTML form entered by the user.

If the input by the user in the input box is e.g. "STACKOVERFLOW" I want the PHP string to be  $username = "STACKOVERFLOW";

Thanks in advance.