PHP: Wait for User Input Before Executing Script - php

Question

I have an html input form as well as a php email script that takes these values on the same page.
The problem is that before I submit any data into the forms I get a blank email because my php script is not waiting for the user input.
I don'y wan't to use another page for my email script because I don't want to pass variables through GET and I don't know how to implement sessions yet.
Thanks and here is my code
<div id = "center">
<form action="post.php" name="emailform" method="post">
<input type="text" name="name">
<input type="text" name="email">
<input type="text" name="message">
<input type="submit" value="Send Email">
</form>
</div>
<?php
if (!isset($_POST['submit'])) {
echo 'you have hit the submit button';
$name = $_POST['name'];
$visitor_email = $_POST['email'];
$message = $_POST['message'];
$email_from = 'trustyclient#yoursite.com';
$email_subject = "Message from client";
$email_body = "Message from: $visitor_email \n \n Message:$message";
$to = "myemail#myemail.com";
$headers = "from:adam\r\n";
mail($to,$email_subject,$email_body,$headers);
} else {
echo 'You have not hit the submit button yet';
}
?>

Answer 1

First, give your submit button a name, like 'submit' (because you've already referenced that name in the PHP). Example:
<input type="submit" name="submit" value="Send Email">
Now you can actually use $_POST['submit'] in your code.
Then another tweak:
When you state if (!isset($_POST['submit'])) {, the following code runs if the submit button has not been pressed, because of the !. To fix, just remove the !, making it:
if (isset($_POST['submit'])) {
! tells the if statement to evaluate to true if the following expression, here isset($_POST['submit']), evaluates to false. Therefore ! means "if the opposite".
NB: Also, the concept that the PHP runs when the submit button is pressed is slightly off. The submit button triggers that page to load a different page (or the same page). The PHP code runs only once when the page loads.

Answer 2

Try this.
<div id = "center">
<form action="post.php" name="emailform" method="post">
<input type="text" name="name">
<input type="text" name="email">
<input type="text" name="message">
<input type="submit" value="Send Email">
</form>
</div>
<?php
if (isset($_POST['submit'])) {
echo 'you have hit the submit button';
if (empty(trim($_POST['name'])) || empty(trim($_POST['email'])) || empty(trim($_POST['message']))) {
echo 'Some fields are empty.';
} else {
$name = $_POST['name'];
$visitor_email = $_POST['email'];
$message = $_POST['message'];
$email_from = 'trustyclient#yoursite.com';
$email_subject = "Message from client";
$email_body = "Message from: $visitor_email \n \n Message:$message";
$to = "myemail#myemail.com";
$headers = "from:adam\r\n";
mail($to,$email_subject,$email_body,$headers);
}
} else {
echo 'You have not hit the submit button yet';
}
?>