Why does one method produce Notice: Undefined index:

Question

I am trying to understand why one method of implementation produces (all the code in a .php file) - Notice: Undefined index:

and putting the same php code snippet into a separate action file and calling it from html does not.

See example code:

File that has an error - php_examp1.php

<!DOCTYPE html>
<html>
    <body>
    <p>Example</p>
        <form method="post">
          <label for="num1"> 1st Number (between 1 and 100):</label>
          <input type="number" id="num1" name="num1" min="1" max="100" step="0.01">
          <input type="submit" value="Submit">
        </form>
        The number entered is:  <?php echo $_POST["num1"]; ?><br>
    </body>
</html>

Files that do not cause an error -php_examp1.html

<!DOCTYPE html>
<html>
    <body>
    <p>Example</p>
        <form action = "action_examp.php" method="post">
          <label for="num1"> 1st Number (between 1 and 100):</label>
          <input type="number" id="num1" name="num1" min="1" max="100" step="0.01"> 
          <input type="submit" value="Submit">
        </form>
    </body>
</html>

File - action_examp.php

The number entered is:  <?php echo $_POST["num1"]; ?><br>

if you call the first example for the first time, there is no post been made... — Honk der Hase, Feb 25 '21 at 16:31
Because when you first open the page, nothing is posted (it's a simple `GET` request). If you directly open `action_examp.php` from the example #2, you'll get the same issue. — El_Vanja, Feb 25 '21 at 16:31
Just as a quick solution - `echo $_POST["num1"] ?? 'Nothing entered';` — Nigel Ren, Feb 25 '21 at 16:33

score 0 · Accepted Answer · answered Feb 25 '21 at 16:41

<!DOCTYPE html>
<html>
    <body>
    <p>Example</p>
        <form method="post">
          <label for="num1"> 1st Number (between 1 and 100):</label>
          <input type="number" id="num1" name="num1" min="1" max="100" step="0.01">
          <input type="submit" value="Submit">
        </form>
        The number entered is:  <?php 
            if(array_key_exists('num1', $_POST)) {
                echo $_POST["num1"]; 
            }
        ?><br>
    </body>
</html>

Why does one method produce Notice: Undefined index:

1 Answers1