If the above code is html (not php) then you have to do it this way:
<input type='radio' name='choice_a' value='<?php echo $answer;?>'>
<input type='radio' name='$quiz_no' value='<?php echo $answer;?>'>
To pass this to another php file for checking / processing enclose fields in form tags and set action attribute (and add a submit button):
<form action="anotherfile.php" method="post">
<input type='radio' name='choice_a' value='<?php echo $answer;?>'>
<input type='radio' name='$quiz_no' value='<?php echo $answer;?>'>
<input type="submit" name="submit" value="Submit">
</form>
broj1
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