Home / Questions / 8430
Accepted
Jhonatan Valencia
Asked: 2020-04-25 19:46:59 +0800 CST 2020-04-25 19:46:59 +0800 CST

problem with switch in php

  • 772

Hi, I'm new to programming. I'm trying to do the basic operations using a radio button, but addition and subtraction don't work for me. I don't understand why.

<form method="POST" action="resultado.php">
  <table>
    <tr>
      <th>Numreo 1</th>
      <td>
        <input type="text" name="n1"></input>
      </td>
    </tr>
    <tr>
      <th>Numero 2</th>
      <td>
        <input type="text" name="n2"></input>
      </td>
    </tr>
    <tr>
      <td>
        <input type="radio" name="operacion" value="suma">Suma</input>
        <input type="radio" name="operacion" value="resta">Resta</input>
        <input type="radio" name="operacion" value="producto">Multiplicacion</input>
      </td>
      <td>
        <input type="radio" name="operacion" value="division">Division</input>
        <input type="radio" name="operacion" value="potencia">Potencia</input>
        <input type="radio" name="operacion" value="modulo">Modulo</input>
      </td>
    </tr>
    <tr>
      <td></td>
      <td>
        <input type="submit" name="enviar" value="ENVIAR"></input>
      </td>
    </tr>
  </table>
</form>
//otra pagina
<?php 
		$n1 = $_POST['n1'];

		$n2 = $_POST['n2'];


		switch ($_POST['operacion']) {
			case 'suma':
					echo "el resultado es ".$n1+$n2;		
				break;
			case 'resta':
					echo "el resultado es ".$n1-$n2;
				break;
			case 'producto':
					echo "el resultado es ".$n1*$n2;
					break;
			case 'division':
					echo "el resultado es ".$n1/$n2;
						break;
			case 'modulo':
					echo "el resultado es ".$n1%$n2;	
						break;
			case 'potencia':
					echo "el resultado es ".pow($n1, $n2);						
						break;								
			default:
				# code...
				break;
		}
		 ?>

php

2 Answers

  1. The problem is in the precedence of operators : the concatenation operator ( .) has the same precedence as the addition ( +) and subtraction ( -) operators and that is why you do not get the result you expected.

    Put the operations in parentheses so there are no such precedence issues , and that will fix the problem:

        switch ($_POST['operacion']) {
        case 'suma':
                echo "el resultado es ".($n1+$n2);      
            break;
        case 'resta':
                echo "el resultado es ".($n1-$n2);
            break;
        case 'producto':
                echo "el resultado es ".($n1*$n2);
                break;
        case 'division':
                echo "el resultado es ".($n1/$n2);
                    break;
        case 'modulo':
                echo "el resultado es ".($n1%$n2);  
                    break;
        case 'potencia':
                echo "el resultado es ".pow($n1, $n2);                      
                    break;                              
        default:
            # code...
            break;
    • 3
  2. Best Answer

    You should at least check that the values ​​arrive before trying to trade them. For example:

    if ( $n1 != "" && $n2 != "" ) {
  swich ...

    Then, always put the mathematical operations in parentheses when you are concatenating with strings to avoid problems and make the code clearer, or better put the result of the operations in a new variable beforehand and then concatenate this one. For example:

    switch ($_POST['operacion']) {
    case 'suma':
        $res = $n1 + $n2;
        echo "el resultado es " . $res;      
        break;
    case 'resta':
        $res = $n1 - $n2;
        echo "el resultado es " . $res;  
        break;

    When problems arise, simplify and do traces / debug.

    • 1