Maybe This is dead-simple stupid question, but how PHP translate our code?
<p>i got this code</p>

<p>`

<pre><code>  //
  // prints out "Hello World!"
  //
  hello_world();   //First call

  function hello_world()
  {
    echo "Hello World!&lt;br/&gt;\n";
  }

  hello_world(); //second call

?&gt;`
</code></pre>

<p>Both of 'hello_world' call will print out the same result. It's easily to understand why the second call will be output 'Hello world', but how the first call output the same where it's been call before the initiation of the function hello_world itself ?</p>
