POST action

<form action="action.php" method="post">
 <p>Your name: <input type="text" name="name" /></p>
 <p>Your age: <input type="text" name="age" /></p>
 <p><input type="submit" /></p>
</form>In the PHP tutorial manual, it says that we can have post action to 
the form itself just like above coding.I would like to know in the real 
projects, can we have action to the same PHP file, since that we only need 
have one filebut not 2 files foe POST request,Your help and information is 
great appreciated,regards,Iccsi,