如果表单POST为空，如何阻止php执行脚本？

Question

I have two input fields and whenever I open my page, it displays errors since at the start user has not entered any input to any of the field (& the errors are displayed because the user input is used in sql queries to retrieve data). I just want to display those two forms at start of the page not the errors. Both inputs are required to execute the Compare button. If user has not entered either one of the inputs it should not send request to php for scripting. I mean the Compare button should send request only if both inputs are filled otherwise it should give a message to user to Type the required fields. How to do this?

$trimUser= trim ($_POST['name']);
if(empty($name) || empty($name2))
{
echo "Enter a name ";
}
else if (isset($_POST['name']))
{   
$name=$_POST['name'];
}
else if (isset($_POST['name2']))
{
$name2=$_POST['name2'];
}

& here is my form:

<form action="index.php" method="POST">
<input class="span3 search-query" placeholder="Type User A" type="text" name="name" id="field"/
<input class="span3 search-query" placeholder="Type User B"  name="name2" type="text"
id="field2"/>
<button class="btn btn-primary" data-loading-text="Loading..." >Compare</button>

Answer 1

I simply got rid all of all the errors by adding this error_reporting(E_ERROR | E_PARSE); at the start of my code. However if anyone want to check display validation error messages , one can do easily by what others have mentioned . i.e By using if($_Post). Anyway ,Thank you everyone for the help.