title: PHP concatenation of strings and arithmetic operations
body: <p>I started learning PHP not too long ago and I ran into this issue:</p>
  
  <pre><code>&lt;?php
  
  $a = 1;
  $b = 2;
  
  echo "$a * $b  = " . $a * $b;
  echo "&lt;br /&gt;";
  
  echo "$a / $b  = " . $a / $b;
  echo "&lt;br /&gt;";
  
  echo "$a + $b  = " . $a + $b;
  echo "&lt;br /&gt;";
  
  echo "$a - $b  = " . $a - $b;
  echo "&lt;br /&gt;";
  </code></pre>
  
  <p>I  get the following output:</p>
  
  <pre><code>1 * 2 = 2
  1 / 2 = 0.5
  3
  -1
  </code></pre>
  
  <p>The last two lines in the output are not what I would expect.</p>
  
  <p>Why is this? How are these expressions evaluated? I'm trying to get a better understanding of the language.</p>