validate form in php - php

Question

I'm trying to validate a form of a test. I get an error in answer.php Basically I want to validate that each question has been answered.
The form:
$sql1="SELECT * FROM ex_question WHERE test_name = '$tid' ORDER BY q_nr";
$result1=mysql_query($sql1);
echo "<form method='post' name='form1' action='answer.php'>";
while($row1 = mysql_fetch_array($result1))
{
$q_nr=$row1['q_nr'];
$q_type=$row1['q_type'];
$question=$row1['question'];
$option1=$row1['option1'];
$option2=$row1['option2'];
$option3=$row1['option3'];
echo "<P><strong>$q_nr $question</strong><BR>";
echo "<BR>";
echo "</p>";
if ($q_type != 'mr') {
if($option1!="") {
echo "<input type='radio' name='question[$q_nr]' value='A'>$option1<BR>";
} else {
echo ''; }
if($option2!="") {
echo "<input type='radio' name='question[$q_nr]' value='B'>$option2<BR>";
} else {
echo ''; }
if($option3!="") {
echo "<input type='radio' name='question[$q_nr]' value='C'>$option3<BR>";
} else {
echo ''; }
} else { // else if not <> mr
if($option1!="") {
echo "<input type='checkbox' name='question[$q_nr][]' value='A'>$option1<BR>";
} else {
echo ''; }
if($option2!="") {
echo "<input type='checkbox' name='question[$q_nr][]' value='B'>$option2<BR>";
} else {
echo ''; }
if($option3!="") {
echo "<input type='checkbox' name='question[$q_nr][]' value='C'>$option3<BR>";
} else {
echo ''; }
} //end else if q_type <> mr
echo "<BR>";
echo "</p>";
} //end while row1
echo "<input type='submit' value='Submit' name='Submit'>";
echo "</form>";
answer.php
foreach($_POST['question'] as $key => $ans) {
if ($ans[] = '') {
echo "answer is empty";
}
}
I get the error: Warning: Invalid argument supplied for foreach() in ......

Answer 1

One thing is that you are assigning the answer rather than checking it, use ==
foreach($_POST as $key => $ans) {
if ($ans == '') {
echo "answer is empty";
}
}
and instead of using
name='question[$q_nr]'
I would use for the radio fields
name='question_{$q_nr}'
and for the checkboxes
name='question_{$q_nr}[]'
On answer.php you should be able to do a print_r($_POST) to check what you are getting.

Answer 2

This is probably because your $_POST['question'] is empty. This is what happens when you try to do this with an empty array.
Whereas your HTML says: name='question[$q_nr]'.
Print the values in the array to see what it contains, use print_r.
Edit: $_POST['question'] IS NOT an array! While $_POST IS an array...
Maybe you should try to do something like this:
foreach ($_POST as $key => $value)
Or do it however you want the result to be displayed.