php - foreach loop doesn't execute -

hi have form takes several answers in checkboxes

<p>select modules take:<br /> module1 <input type="checkbox" name="modules" value="module1"/><br /> module2 <input type="checkbox" name="modules" value="module2" /><br /> module3 <input type="checkbox" name="modules" value="module3" /><br /></p> 

now in response page have foreach loop, doesn't execute anything

foreach ($modules $selected){     print "<p>modules ".$selected."</p>"; }; 

any this? in advance

if name checkboxes this, array (with brackets [])

<input type="checkbox" name="modules[]" value="module1"/> 

and of course need iterate correct array:

foreach($_post['modules'] $selected) {