在PHP代码中正确放置函数

Question

我喜欢通过正确的方式编写简洁的代码。这是我的问题，当编写PHP代码（程序）时，你将函数调用与函数定义放在一起。

例如：

if( isset( $_POST['submit_form'] ) )
{
 //Here is function definition 
 test_input($data)
  {
     $data = trim($data);
     $data = stripslashes($data)
     .......
 }
 //Here I am making function calls
  $name = test_input( $_POST['username'] );
  $emailid = test_input( $_POST['useremail'] );

和

 if( isset( $_POST['submit_form'] ) )
{

 //Here I am making function calls
  $name = test_input( $_POST['username'] );
  $emailid = test_input( $_POST['useremail'] );

  //Here is function definition
 test_input($data)
  {
     $data = trim($data);
     $data = stripslashes($data)
     .......
 }