Assitance with basic Calculator

Beginners - Learning PHP
#1

Below I made a basic calculator that adds, subtracts, divides, and multiplies. The issue is, when I submit the values the results do not “echo” on the page. Below is the code i have created. Hoping someone can assist me with this one.


<html>
      <body>

 <form action = "site.php" method="post">

   First number: <input type="number" name="digit1"> <br>
   OP: <input type="text" name="op"> <br>
   Second number: <input type="number" name="digit2"> <br>
 <input type="submit"><br>

</form>

<?php
  $digit1 = $_Post["digit1"];
  $digit2 = $_Post["digit2"];
  $op = $_Post["op"];

if($op == "+"){
  echo $digit1 + $digit2;
} elseif($op == "-"){
  echo $digit1 - $digit2;
}elseif($op == "*"){
  echo $digit1 * $digit2;
}elseif($op == "/"){
  echo $digit1 / $digit2;
}else{
  echo "invalid operator";
}
 ?>

  </body>
</html>
#2
  • $_Post should be $_POST
  • Keep your php block on top and leave HTML on the bottom. Just echo variabeles between HTML like so:
<?php
 $name = 'Don';
 // ...
?>
<!doctype html>
<html>
    <head>
        <title>Hello world</title>
    </head>
    <body>
        <h1>Hello <?php echo $name; ?></h1>
    </body>
</html>
  • $_POST form variables do ONLY exist if you submit your form and the browser request the page again with the POST request method instead of the GET method. A good practice is to make a if statement that tests if the page is called in POST method before accessing your $_POST form variables.
if($_SERVER['REQUEST_METHOD'] == 'POST') {
    // Now we can use the $_POST variables from our form
}
1 Like
#3

Bonus tip: to debug and see what will be inside the $_POST array you could use this line:

echo '<pre>' . print_r($_POST, true) . '</pre>';
1 Like
#4

More bonus tips:

  1. Stop creating variables for nothing
  2. Never trust user input. Escape the form output with htmlspecialchars
#5

Thank you All, your advice was on point, and my calculator is working!

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