posting a search result in php - php

Question

I have created a search using php so that when a user is logged in they can search for other users and add them as a friend. When the user clicks the add as friend button I would like to post the username of the user that is logged in and the username of the user in the search result to a database table called friend_request.
Here is my code
<?php
if(isset($_POST['search'])) {
$search = $_POST['search'];
$search = preg_replace("#[^0-9a-z]i#","", $search);
$search = "%$search%";
if ($stmt = $db->prepare("SELECT username, name, location, gender, date_of_birth, url FROM Users WHERE name LIKE ?")){
$stmt->bind_param("s", $search);
$stmt->execute();
$stmt->bind_result($username, $name, $location, $gender, $date_of_birth, $picture);
$stmt->store_result();
$count = $stmt->num_rows;
if ($count == 0) {
$output = "There was no search results!";
} else {
while ($stmt->fetch()) {
$output .='<form action="#" method="post"><div class="row"><div class="col-sm-3">'.$name.'<br>'.$location.'<br>'.$gender.'<br>'.$date_of_birth.'</div>';
$output2 = '<div class="col-sm-3"><img src="upload/'.$picture.'"width="180" height="144" /></div>';
$output3 = '<input type="submit" name="addfriend" value="Submit" /></div></form>';
}
}
}
}
if(isset($_POST['addfriend'])) {
$user_from = $_SESSION['username'];
$user_to = $_POST['username'];
if ($stmt = $db->prepare("INSERT INTO `friends_request`(`user_to`, `user_from`) VALUES (?,?)")){
$stmt->bind_param("ss", $user_to, $user_from);
$stmt->execute();
}
}
?>
When I run my code I get the following message
Notice: Undefined index: username in /Applications/MAMP/htdocs/student_connect/header.php on line 51

Answer 1

It is simple.
It says $_SESSION['username']; hasn't been set, so look for the line of code where you expect you'd set it. I guess it might be in some other file (maybe to be executed after a login-form filling..?)

Answer 2

You need to start Debugging your code.....
Try adding this line after "$user_from = $_SESSION['username'];"
if(!$user_from)
{
echo "<pre>";
var_dump($_SESSION);
echo "<pre>";
}
Run your code and paste the results here - we can then start to determine what information is held in SESSION.
This is something you have to do when code doesn't do what expected, check your variables and see whats missing before heading to Stack. We are here to help, but need all info possible.