Unique value in array.. i.e. in nested array

I came across one limitation of array_unique: it doesn't work properly if you have arrays inside your main array.

The reason is that to compare two values, the function tests if (string) $value1 == (string) $value2. So if $value1 and $value2 are both arrays, the function will evaluate the test to 'Array' == 'Array', and decide that the $values are repeated even if the arrays are different.

So a work around is to find a better conversion of an array to a string, which can be done with json:

print "define an array with repeated scalar '1' and repeated 'array(1)':";
$a_not_unique = array(
    'a' => 1,
    'b' => 1,
    'c' => 2,
    'd' => array(1),
    'e' => array(1),
    'f' => array(2),
);
print_r($a_not_unique);

print "try to use simply array_unique, which will not work since it exludes 'array(2)':";
$a_unique_wrong = array_unique($a_not_unique);
print_r($a_unique_wrong);

print "convert to json before applying array_unique, and convert back to array, which will successfully keep 'array(2)':";
$a_unique_right = $a_not_unique;
array_walk($a_unique_right, create_function('&$value,$key', '$value = json_encode($value);'));
$a_unique_right = array_unique($a_unique_right);
array_walk($a_unique_right, create_function('&$value,$key', '$value = json_decode($value, true);'));
print_r($a_unique_right);
?>

Results:
define an array with repeated scalar '1' and repeated 'array(1)':
Array
(
    [a] => 1
    [b] => 1
    [c] => 2
    [d] => Array
        (
            [0] => 1
        )

    [e] => Array
        (
            [0] => 1
        )

    [f] => Array
        (
            [0] => 2
        )
)

try to use simply array_unique, which will not work since it exludes 'array(2)':
Array
(
    [a] => 1
    [c] => 2
    [d] => Array
        (
            [0] => 1
        )
)

convert to json before applying array_unique, and convert back to array, which will successfully keep 'array(2)':
Array
(
    [a] => 1
    [c] => 2
    [d] => Array
        (
            [0] => 1
        )

    [f] => Array
        (
            [0] => 2
        )
)

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Using cURL with PHP

The background

If you write a PHP program that is designed to go and fetch a webpage from the World Wide Web you soon find out that you are not allowed to because of a sensible restiction placed on the use of fopen(), simplexml_load_file and the like.
This restiction is absolutely vital to maintain the integrity of a shared server system and you would have to be ten bob short of a quid to allow the retrieval of all that untrusted material from the web. So an intermediate step is used.
But cURL looks complicated, especially to me, and it just looks like something else to learn. But all you need is that webpage being fetched, so you only need a bit of cURL code to do that. The good news is that it has already been written. The bad news is that it is not obvious where to stick it!

The PHP portion

(save as rsayahoo.php)

$xml = simplexml_load_file('http://rss.news.yahoo.com/rss/oddlyenough');
print "
\n"; foreach ($xml->channel->item as $item){   print "
$item->title
\n"; } print "
";
?> 

The cURL portion

But the simplexml_load_file in the function is not allowed out into the wild. So you need an intermediary step, cURL, to go and fetch the page.
So the cURL sample would be.

(save as geturl.php)

$ch = curl_init("http://rss.news.yahoo.com/rss/oddlyenough");
$fp = fopen("example_htmlpage.html", "w");

curl_setopt($ch, CURLOPT_FILE, $fp);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_exec($ch);
curl_close($ch);
fclose($fp);
?> 

After the cURL portion has executed.

(upload as localrsayahoo.php)

$xml = simplexml_load_file('example_htmlpage.html');
print "
\n"; foreach ($xml->channel->item as $item){   print "
$item->title
\n"; } print "
";
?>

 

Adding the cURL and PHP portions together

Although the two programs (the cURL part and the PHP) have been shown as two seperate actions you could of course combine them into one program.

$ch = curl_init("http://rss.news.yahoo.com/rss/oddlyenough");
$fp = fopen("example_homepage.html", "w");

curl_setopt($ch, CURLOPT_FILE, $fp);
curl_setopt($ch, CURLOPT_HEADER, 0);

curl_exec($ch);
curl_close($ch);
fclose($fp);

$xml = simplexml_load_file('example_homepage.html');
print "
\n"; foreach ($xml->channel->item as $item){   print "
$item->title
\n"; } print "
";

?>

Replacement function for simplexml_load_file

This function uses the CURLOPT_RETURNTRANSFER option, so you don't have to write the results to a local file to retrieve them.

function My_simplexml_load_file($URL)
  {
  $ch = curl_init($URL);

  curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
  curl_setopt($ch, CURLOPT_HEADER, 0);

  $xml = simplexml_load_string(curl_exec($ch));

  curl_close($ch);

  return $xml;
  }

?>

Starting , storing and destroying Session Variables in PHP

Sessions are used in PHP in various types of applications to pass data and maintain state of the user. If you are using any membership system where user has to login then after verification we have to keep the login status throughout, so we can maintain the authenticity. To do this we have to use session variables as we will store the userid inside this. Similarly for a shopping cart script we have to store the selected items of the user in session variable and display it to the visitor when required. Sessions are the unique link between the user and the server so all actions of the user can be personalized to the user and handled by the server.

We will study how to start a session, how to store variables in a session, how to destroy a session and other related functions for session handling with examples.

Here in many scripts we have used sessions and you can use them as an example. Member signup and login script uses them very often. You can download different scripts and read the code to understand how the sessions are used.

Please note that session are handled differently in PHP 5 and above so we will stick to this version only. If you are using PHP 4 then there is small difference in functions ( or syntax ) but the basic concept remains same.

Starting a session

We have verified that user entered login id and password is matching so we will give access by keeping the user id in session variable. Here is the code.

session_start();
$_SESSION['userid']=$userid;

Note that first line session_start(); this line has to be at the top of your page or this function is to be used before we send any data to the browser. The second line actually stores the data to the session variable, this can be any where within the page. The variable $userid stores the user id ( say bigstar ) now the same value is available in our session. Now let us see how to display or use this session variable.

Displaying or using a session variable

As the member has logged, its user id we can display by showing a welcome message. Here is an example.

echo “Welcome $_SESSION[userid]”;

Note that we must use the function session_start() at the starting of the page ( before sending any output to browser ) to use any session variables. We can check the existence of session with userid at every page level which are supposed to be used by logged in members.

if(!isset($_SESSION['userid'])){
echo "Sorry, Please login and use this page";
exit;
}

As you can see we have used isset function to check the presence of session variable storing userid. If the variable does not exist then we are displaying a message asking the user to login and then terminating the script by using exit command. This part of the script you can see in detail at our login and logout script.

Displaying all the session variable.

We can store different data in session variables. In our example we have used only one ( that is $_SESSION[userid] ) but we can store other data also. Let us add name to the session variable like this.

$_SESSION['name']="Ronny";

Now we can display all the elements of the session array and see what are the session variables created and what data they store.

while (list ($key, $val) = each ($_SESSION)) {
echo "$key -> $val
";
}

you will get a list like this.

userid -> plus2net
name -> Ronny

Destroying the session

To destroy or delete the sessions we can use these two commands. It is advisable to use these commands in this sequence to destroy remove sessions in PHP.

session_unset();
session_destroy();

Important : Don't forget to give session_start() command at the staring of the page.
You can test all the above code to learn and understand how the session works by running these sample codes at your system. Open the index.php file and rest you can easily understand.

APC caching for Web services - Yahoo

error_reporting(E_ALL);

$request =  'http://search.yahooapis.com/ImageSearchService/V1/imageSearch?appid=YahooDemo&query=Madonna&results=1';

// Number of seconds until the cache gets stale
$cache_timeout = 7200;

// Check the cache
$response = request_cache($request, $cache_timeout);

if ($response === false) {
 die('Request failed');
}

// Output the XML
echo htmlspecialchars($response, ENT_QUOTES);

// This is the main caching routine. More robust error checking should
// be implemented.

function request_cache($url, $ttl) {
 if(!$xml = apc_fetch($url)) {
  $xml = file_get_contents($url);
  if ($xml === false) return false;
  apc_store($url,$xml, $ttl);
 }
 return $xml;
}

?>

PHPfundamentals Series: A Background on Statics (Part 1 on Statics)

Just beyond reading the title, you’ve more than likely come to this article as the curious yet uninformed, the mad and raving lunatic, or as an enlightened one. Static class members (from here on called simply, “statics”) in PHP conjure both the best and worst in developers for a variety of reasons. In part 1 of this series of articles on statics, we’ll explore some background to get a better understanding of statics in PHP.

Some Static Background And Understanding

Before we can move into the arguments that surround statics, we first need to understand what they are in the context of PHP.  The core of the PHP language and runtime can draw some pretty big corollaries from the Java/JVM and C#/.NET language platforms. The biggest, and most important for the purposes of this article, is PHP’s object model. Like Java and .NET, PHP follows a class-based, single-inheritance, multiple-interface model- a tenet described by the grandfather of OO languages: smalltalk. Of course, PHP applies its own “perspective” when it comes to the actual implementation details in that of typing, casting, mixed-paradigm usage, and so on; but the foundation for the object model is clearly defined.
That said, it is easy for the PHP community to draw comparisons and, more importantly, “borrow” best practices from both the Java and .NET communities. We certainly have borrowed our fair share with regards to development time tools, infrastructure tools and design patterns. Over the past 5 to 7 years, there has been an increasing adoption of best practices and patterns from the enterprise Java community, particularly in the form of two major texts: GoF and PoEAA. The GoF (Gang of Four) text primarily discusses best practices in the form of code structure and reuse: factory, singleton, adapter, composite, facade, iterator and observer to name a few. PoEAA (Patterns of Enterprise Application Architecture), on the other hand, attempts to solve higher order problems, particularly architectural problems at the application layer: MVC, Page Controller, Front Controller, Domain Model, Table and Row Gateway, and so on. While the examples are primarily executed in Java, they are structurally similar when implemented in PHP, so much so that PHP developers can read the Java examples as pseudo-code. This is what makes these patterns so applicable and thus popular in the PHP community.
Since we now know where these usage patterns originated, we should have a look at the target language platform: PHP. The key concept which delineates the PHP platform from the JVM and .NET platforms, is that PHP by default assumes a shared-nothing architecture. What does this mean? It means out of the box, PHP is not a persistent application platform. PHP’s runtime is built around the notion of primarily solving the web problem. In turn, since the web is request driven, you might say that an application written in PHP is also request driven. Put another way, the scope of your application is bound to a single request. The shared-nothing aspect means that the state of the application is built-up and torn-down upon the start and completion of each request to your application. Conversely, Java and .NET offer a persistent application stack which means the application’s state exists separate from the requests that come in via the web server. So, in PHP, the many requests each contain a single running instance of your application. In Java/.NET, the single application running handles the many requests.

Statics in Analogies

Still don’t get it? Let’s talk in a couple of analogies. Let’s assume we’ve built a basic application with the “out-of-the-box” technologies offered; one built on top of PHP and the other built on top of Java (or .NET, you can choose.) With your Java/.NET application, if a request is never received from your web server, the application is indeed still running. In PHP, if a request is never received from your web server, the application has NEVER run. The runtime of a Java/.NET application might be hours or days, whereas the runtime of a PHP application is a long as it takes to service the request. This analogy’s mileage may vary, and it is surely intended for demonstrative purposes. You could inject any number of monkey wrenches into it, but for all intents and purposes- it’s correct and it works.
Understanding the full scope of an applications runtime state is the most important aspect into understanding the role of static class members in OO programming. Static class members live as long as the application runtime is valid and alive. What this means it is that any class member state that has been set during any operation during the applications runtime will persist until the application ceases to exist. Looking back at our main platform differences, we can see that in the Java/.NET platform, statics members created in the scope of an application layer will be around until someone pushes the “shutdown” button on that application. This could mean a static member or static state is persisted for hours, days, or even longer. Like these persistent application stacks, PHP will destroy any static members and state at the end of the applications lifecycle. Unlike these persistent application stacks, the application lifecycle ends with the completion of a web request. This means that static members and static state in PHP, for the average web application, sticks around for seconds or less and is only valid in the context of a single web request.

Statics in Pictures

Still don’t get it? Lets have a look at a few images to better explain these concepts.
The following images will attempt to explain the various layers of a web application, one from the perspective of the JVM/.NET platform, the other from the perspective of the PHP platform. (For all intents and purposes, the PHP platform could also be any scripting language executed by an apache module or fastcgi.)
The green layer is the web server layer, this is the process that will attach to port 80 and listen for requests. The blue layer represents the application process itself. This layer is responsible for global application state and class-based static state. The orange layer is a request which comes in from the web, this is typically what we’ve called a page request. Inside of each web request is the yellow layer, which represents the page-lifecycle. In terms of the application, this is where all of the request specific application routines happen including page startup and business logic.

Contrasted against …

The most important thing to take away from these images, particularly with respect to understanding statics, is the blue layer, or the layer that best represents the scope of globals and static members. This is the heart of what is meant by a “shared-nothing” architecture. It is this key difference that affects how we architect the code for our web applications.
In the next article in this series, we’ll have a look at PHP’s application architecture in greater detail and how it solves problems that might arise from a shared-nothing style architecture, why this architecture is arguably better for the web and cloud based services, but most importantly, how statics fit into this paradigm.

PHP Cookies

A cookie is often used to identify a user.

---

What is a Cookie?

A cookie is often used to identify a user. A cookie is a small file that the server embeds on the user's computer. Each time the same computer requests a page with a browser, it will send the cookie too. With PHP, you can both create and retrieve cookie values.

---

How to Create a Cookie?

The setcookie() function is used to set a cookie.
Note: The setcookie() function must appear BEFORE the tag.

Syntax

setcookie(name, value, expire, path, domain);

Example 1

In the example below, we will create a cookie named "user" and assign the value "Alex Porter" to it. We also specify that the cookie should expire after one hour:

setcookie("user", "Alex Porter", time()+3600);    ?> .....

Note: The value of the cookie is automatically URLencoded when sending the cookie, and automatically decoded when received (to prevent URLencoding, use setrawcookie() instead).

Example 2

You can also set the expiration time of the cookie in another way. It may be easier than using seconds.

$expire=time()+60*60*24*30; setcookie("user", "Alex Porter", $expire); ?> .....

In the example above the expiration time is set to a month (60 sec * 60 min * 24 hours * 30 days).

---

How to Retrieve a Cookie Value?

The PHP $_COOKIE variable is used to retrieve a cookie value.

In the example below, we retrieve the value of the cookie named "user" and display it on a page:

// Print a cookie echo $_COOKIE["user"]; // A way to view all cookies print_r($_COOKIE); ?>

In the following example we use the isset() function to find out if a cookie has been set:

if (isset($_COOKIE["user"]))   echo "Welcome " . $_COOKIE["user"] . "! "; else   echo "Welcome guest! "; ?>

---

How to Delete a Cookie?

When deleting a cookie you should assure that the expiration date is in the past.
Delete example:

// set the expiration date to one hour ago setcookie("user", "", time()-3600); ?>

---

What if a Browser Does NOT Support Cookies?

If your application deals with browsers that do not support cookies, you will have to use other methods to pass information from one page to another in your application. One method is to pass the data through forms (forms and user input are described earlier in this tutorial).
The form below passes the user input to "welcome.php" when the user clicks on the "Submit" button:
Retrieve the values in the "welcome.php" file like this:

Name:
Age:

Welcome .

You are years old.