How to perform arithmetic operations inside concatenating string in PHP? : <p>This code:</p>

<pre><code>$a = "100";
echo "abc" . $a - 1;
</code></pre>

<p>prints out <code>-1</code> instead of <code>abc99</code>.</p>

<p>Obvious workaround would be:</p>

<pre><code>$a = "100";
$tmp = $a - 1;
echo "abc" . $tmp;
</code></pre>

<p>But is there a way to calculate <code>$a - 1</code> without creating temporary variable?</p>
