I am working on a class assignment where we need to pick a formula with two or more variables and write a script to solve the formula after inputting the variables. I chose the quadratic formula because it’s my favorite. I want it to post a message when non-numeric values are inputted or left blank and a different message if the A variable is zero. The first error message works, but it still displays that message when A = 0. I am using elseif for the A = 0 condition, but it seems to just skip this. Here is my code:

// Gets the data from the form

$avar = $_POST[‘avar’];

$bvar = $_POST[‘bvar’];

$cvar = $_POST[‘cvar’];

// This solves for x

```
if ( empty($avar) or empty($bvar) or empty($cvar) || !is_numeric($avar) or !is_numeric($bvar) or !is_numeric($cvar)) {
$answer = 'All variables must be numbers.';
include('index.php');
exit();
```

}

else if ( $avar == 0 ) {

$answer = ‘This is a linear equation, not a quadratic equation.’;

include(‘index.php’);

exit();

}

else {

$radical = pow($bvar, 2) - (4 * $avar * $cvar);

$denom = 2 * $avar;

$numer1 = -($bvar) + sqrt($radical);

$numer2 = -($bvar) - sqrt($radical);

$xans1 = $numer1 / $denom;

$xans2 = $numer2 / $denom;

// This shows the results

```
$answer = 'x = '.number_format($xans1, 2).', '.number_format($xans2, 2);
}
```