php - Is there a way to subtract two variables inside an echoed variable?

I am trying to subtract two variables which are in another variable and every time i try there is an error saying "Warning: A non-numeric value encountered". I can do multiplication, addition and even divide the variables but somehow subtraction is giving an error. Below is the code.

$first = 2;
$second = 4;

$answer.='<p>The answer is '.$first - $second.'</p> ';
echo $answer;

Solution:

Subtract both values into one variable before. You can then echo that one.

$first = 2;
$second = 4;
$result = $first - $second;

$answer.='<p>The answer is '.$result.'</p> ';
echo $answer;

Or put () around the calculation if you want to do it quick and dirty:

$answer.='<p>The answer is '.($first - $second).'</p> ';

Solution:

echo '<p>The answer is '. ($first - $second) .'</p> ';


//Output "The answer is -2"

Solution:

Just set parentheses () arround your calculation.

<?php
 $first = 2;
$second = 4;

$answer.='<p>The answer is '.($first - $second).'</p> ';
echo $answer;