How do I receive data from a form that has repeated field names?

  

When you put a "name" with [] brackets it is sent in array form to the receiver.

//o array
$alternativa = $_POST['alternativa'];
//Retorna o número de elementos da array:
$result = count($alternativa);

for ($i = 0; $i < ($result) ; $i++) {
  echo " Alternativa " . $alternativa[$i] . "<br>";
}

  

Regarding the control structure:

• Expresses 3 expressions at the beginning of the for         
  • Being the 1st expression evaluated only once . Usually used to create the control variable.
              
  • 2nd expression is evaluated at the beginning of each iteration, if this expression returns false the looping is terminated. It can be considered the conditional of the for.
              
  • 3rd Expression is evaluated at the end of each iteration, usually used to change the value of the control variable.
          
    
• Separate expressions using the; (semicolon).
    
• Looping runs as long as the condition of the 2nd expression is true (True)
    
• When the condition of the 2nd expression evaluates to false (False), the processing of the routine is diverted out of the loop
    
• The looping code block must be enclosed by braces {}
    
• End the code referring to the block in 4 spaces for readability, how to configure your text editor to transform Tabs into spaces
    
• We use a counter for looping not to be an infinite looping, this is declared in the 1st expression
• Do not forget to change the value of the counter in the 3rd expression so that we do not fall into an infinite looping.