title: Concatenate PHP function output to a string like variables
body: <p>For variable <code>$x</code> we can concatenate it to a string in many ways, one of them is like the following:</p>
  
  <pre><code>$x = "Hello";
  echo "I say {$x} to all of you.";
  // The output should be: I say Hello to all of you.
  </code></pre>
  
  <p>However, If I tried to do something like this with a function, it will fail:</p>
  
  <pre><code>$x = "Hello";
  echo "I say {strtolower($x)} to all of you.";
  // The output should be: I say {strtolower(Hello)} to all of you.
  </code></pre>
  
  <p>If there is a synonym way just like used for the variable, I will be appreciated to know it. In other words, I don't want to split the main string and I don't want to use <code>sprinf</code>.</p>