[SOLVED] if problem?

[robert_gsfame]

guys, i got confused with the code below:

 

what i want is that when user choose radiobutton1 (radio1) then textbox4 (txt4) (value=yes) can left empty but if not, then textbox4 (txt4) cannot left empty

 

this code doesn't work well as when radiobutton1 not chosen (let say i choose radiobutton2 (value='no')) , textbox4 still cannot left empty

 

if(((isset($_POST['submit']))&&(!empty($_POST['txt1']))&&(!empty($_POST['txt2']))&&(!empty($_POST['txt3']))&&((($_POST['radio1'])=='yes')&&(!empty($_POST['txt4']))){

 

echo "complete";}

 

thx for any helps