Need help with PHP homework - friend matching algorithm - php

Question

I'm totally new to php and have started learning it. I have two homework assignments in php and html.
Assignment 1:
I have to store some people's names and all of their friends names. I have to list only people who have common friends. My problem is that if a person has no friends in common with someone else I get a message "Rana has 0 friends in common with Roni. I do I prevent this:
Assignment 2:
I have a html form to search for a person from the last php file
When I will search for Rana the PHP form will open and and print:
Rana have 4 friends and he has a common friend with Nandini and Mamun.
When I search for Tanmoy the page will be open and print:
Tanmoy is Rana’s friend who has 4 friends and common friends with Nandini and Mamun.
For this I have to used the function “post/get/request”
Here is my code so far:
<?php
# Function: finfCommon
function findCommon($current, $arr) {
$cUser = $arr[$current];
unset($arr[$current]);
foreach ($arr As $user => $friends) {
$common = array();
$total = array();
foreach ($friends As $friend) {
if (in_array($friend, $cUser)) {
$common[] = $friend;
}
}
$total = count($common);
$add = ($total != 1) ? 's' : '';
$final[] = "<i>{$current} has {$total} friend{$add} in common with {$user}.</i>";
}
return implode('<br />', $final);
}
# Array of users and friends
$Friends = array(
"Rana" => array("Pothik", "Zaman", "Tanmoy", "Ishita"),
"Nandini" => array("Bonna", "Shakib", "Kamal", "Minhaj", "Ishita"),
"Roni" => array("Akbar", "Anwar", "Khakan", "Pavel"),
"Liton" => array("Mahadi", "Pavel"),
"Mamun" => array("Meheli", "Tarek", "Zaman")
);
# Creating the output value
$output = "<ul>";
foreach ($Friends As $user => $friends) {
$total = count($friends);
$common = findCommon($user, $Friends);
$output .= "<li><u>{$user} has {$total} friends.</u><br /><strong>Friends:</strong>";
if (is_array($friends) && !empty($friends[0])) {
$output .= "<ul>";
foreach ($friends As $friend) {
$output .= "<li>{$friend}</li>";
}
$output .= "</ul>";
}
$output .= "{$common}<br /><br /></li>";
}
$output .= "</ul>";
# Printing the output value
print $output;
?>

Answer 1

For the assignment 1.1: You have just to filter out the unwantend responses with an
if ($total>0) {
$output .= "<li><u>{$user} has {$ ...
}
clause.
For the second assignment:
You have to create a page that expects a parameter to be read via $_GET or $_POST or $_REQUEST (call it name, for example). They are not functions, are arrays and you can access them from every scope in you program (they are superglobals and you don't need to declare them with gobals).
I would just print a select with the known people if the name (eg. $_REQUEST['name'] )is missing just print the form, otherwise find the person indicated by the input and print the result of the search.
EDIT:
For the second assignment, you will have to figure how to get the input data.
Probably I will use an approach a bit different
Provided that you have a form similar to this
<form action="homework.php" method="get">
Person: <select name="searchperson" />
<option> </option>
...
<option> </option>
</select>
</form>
you will have to get the list of all the known peoples in a manner similar to this:
$friends = array(
"Rana" => array("Pothik", "Zaman", "Tanmoy", "Ishita"),
"Nandini" => array("Bonna", "Shakib", "Kamal", "Minhaj", "Ishita"),
"Roni" => array("Akbar", "Anwar", "Khakan", "Pavel"),
"Liton" => array("Mahadi", "Pavel"),
"Mamun" => array("Meheli", "Tarek", "Zaman")
);
// create a flat array with all the known peoples
$knownPeople = array_reduce(
$friends,
function($current, $result) {
return array_merge($result, $current);
},
array_keys($friends)
);
$knownPeople = array_flip(array_flip($knownPeople)); //get rid of duplicates
asort(knownPeople); // sort the names
$knownPeople = array_values($knownPeople); // normalize the array indexes
and then get the form you need with a function like this:
function theForm($people) {
$options = '<option>'.join("</option>\n<option>",$people). '</option>';
echo "
<form action=\"homework.php\" method=\"get\">
<h2>Chose the people you want investigate on:</h2>
Person: <select name=\"person\" />
$options
</select>
</form>";
}
Whenever you get a grasp on the previous code or not, you have to evaluate the input and take the opportune actions:
Let say that your script is called homework.php (you will see the name into the action of the form) and it is located ad http://example.com. His URI will be http://example.com/homework.php
There are several possible scenarios:
the user call the script for the first time
the user choose a person from the select
the user invoke your script manually with a known person as parameter
the user invoke your script manually with a person you don't have in your list
Let's review the different cases:
the user call the script for the first time
What appened: the user go to http://example.com/homework.php crossing a link or writing the URI into the browser address bar.
How you detect this scenario: Given the form above you can check $_GET['person']. if it is not isset or empty or not array_key_exists you can state you are into the first scenario.
To do: Just output the form and exit.
the user choose a person from the select
What appened: the user get the form (first scenario) and choose a name from the select.
How you detect this scenario: The detection of the first scenario fails and you can find the name contained into $_GET['person'] into the knownPeople array.
To do:
sanitize the input (remove any spurious character)
find the name into the knownPeople array to be sure you are not serving a forged request
apply your functions to the person in input in order to get the desired output
output the result you got
the form for a new query or a link to http://example.com/homework.php
the user invoke your script manually with a known person as parameter
What appened: the user use a URI like http://example.com/homework.php?person=Rana to reach the script
How you detect this scenario: If the method you use in the form is get you can't (at least not using this simple scenarion) and you won't bother to as it can be considered a legal request as this is an homework and you don't have requirements about it. If you used the method post you have the chance to detect the forgeries as the parameter passed with that method are usually stored into the $_POST array. You can still find the name contained into $_GET['person'] into the knownPeople array.
To do: Same as second scenario
sanitize the input (remove any spurious character)
find the name into the knownPeople array to be sure you are not serving a forged request
apply your functions to the person in input in order to get the desired output
output the result you got
the form for a new query or a link to http://example.com/homework.php
the user invoke your script manually with a person you don't have in your list
How you detect this scenario: The detection of the first scenario fails and you can not find the name contained into $_GET['person'] into the knownPeople array.
To do:
sanitize the input (remove any spurious character)
find the name into the knownPeople array to be sure you are not serving a forged request
as the check fails output an error messages stating the user is unknown and let the user go to the correct uri with a link to http://example.com/homework.php.
Not all forgeries are bad. Consider an user that make a legal search and bookmark the result. If the list of friends change and then he returns to the page using the bookmark. He will fall straight into the fourth scenario
Hope this will help you to comprehend how the php scripting works.

Answer 2

change findCommon function from
function findCommon($current, $arr) {
$cUser = $arr[$current];
unset($arr[$current]);
foreach ($arr As $user => $friends) {
$common = array();
$total = array();
foreach ($friends As $friend) {
if (in_array($friend, $cUser)) {
$common[] = $friend;
}
}
$total = count($common);
$add = ($total != 1) ? 's' : '';
$final[] = "<i>{$current} has {$total} friend{$add} in common with {$user}.</i>";
}
return implode('<br />', $final);
}
to
function findCommon($current, $arr) {
$cUser = $arr[$current];
unset($arr[$current]);
foreach ($arr As $user => $friends) {
$common = array();
$total = array();
foreach ($friends As $friend) {
if (in_array($friend, $cUser)) {
$common[] = $friend;
}
}
$total = count($common);
$add = ($total != 1) ? 's' : '';
if ( $total > 0 ) $final[] = "<i>{$current} has {$total} friend{$add} in common with {$user}.</i>";
}
return implode('<br />', $final);
}
The change is i added a if ( $total > 0 ) before $final[] = ..
for the second one.
<?php
function searchPerson($person, $friends){
$direct = false;
$found = false;
if ( in_array ($person, array_keys($friends) ) ){
list($total, $common_friends) = commonFriend ($person, $friends);
$direct = true;
$found = true;
}
else{
foreach ( $friends as $friend => $his_friends ){
if ( in_array ( $person, $his_friends ) ){
list($total, $common_friends) = commonFriend ($friend, $friends);
$direct = false;
$found = true;
$friend_person = $friend;
break;
}
}
}
if ( !$found ) return false;
$output = $person . " ";
if ( $direct ){
$output .= " has " . $total . " friends";
}
else{
$output .= " is " . $friend_person . "'s friend who has " . $total . " friends";
}
if ( isset($common_friends[0]) ) $output .= " and common friends with " . $common_friends;
return $output;
}
function commonFriend ($person, $friends){
$my_friends = $friends[$person];
unset($friends[$person]);
$total_friends = count($my_friends);
$common_with = array();
foreach ( $friends as $friend => $his_friends ){
foreach ( $my_friends as $my_friend ){
if ( in_array ($my_friend, $his_friends) ){
$common_with[] = $friend;
}
}
}
$common_with = array_unique ($common_with);
$common_friends = "";
if ( count($common_with) > 0 ){
$common_friends = join (", ", $common_with );
}
return array ( $total_friends, $common_friends );
}
$friends = array(
"Rana" => array("Pothik", "Zaman", "Tanmoy", "Ishita"),
"Nandini" => array("Bonna", "Shakib", "Kamal", "Minhaj", "Ishita"),
"Roni" => array("Akbar", "Anwar", "Khakan", "Pavel"),
"Liton" => array("Mahadi", "Pavel"),
"Mamun" => array("Meheli", "Tarek", "Zaman")
);
$person = $_GET['person'];
$output = searchPerson($person, $friends);
if ( $output === false ) print $person . " is not on the list";
else print $output;
?>
What you have to do with the second assignment is you need a form.
lets say the above code was named searchPerson.php
then add a html page like
<html>
<head>
<title>Search for friend</title>
</head>
<body>
<form action="searchPerson.php" method="get">
Person: <input type="text" name="person" /><input type="submit" value="search" />
</form>
</body>
</html>
or run directly like
searchPerson.php?person=Rana
And why you get a message like that is because $person = $_GET['person']; gets the person name from the url, and u must have run it like searchPerson.php, so their is no value for $person to check.
-- EDIT
Chaged the code to work with people not in the list