Tag Archives: PHP

Have you ever come across a PHP class that connects methods together in a single line to achieve some goal? (If you haven’t, Guzzle and SwiftMail are a couple of examples.)

//Example from http://guzzlephp.org/
$client = new Client($url);
$request = $client->get('/user')->setAuth('user', 'pass');
$response = $request->send();

jQuery also operates in a similar manner, using the same principle. The technique is called method chaining, and is quite useful in cases where a class has many public methods that could be called upon with each others’ output.

If you wanted, the above example could conceivably be rewritten like this:

$client = new Client($url);
$path = $client->get('/user');
$request = $path->setAuth('user', 'pass');
$response = $request->send();

This works because of the way chainable methods are set up. The secret to making it work is that every method must return the entire object. What you’re doing when you chain Method A with Method B ($object->methodA()->methodB) is calling Method B from the object returned by Method A, which it returned from the object that called it to begin with.

Here’s an example class that permits chaining, since there’s no way that code could be more syntactically awkward than that sentence:

class MyClass {

	function __construct() {
		$this->thing = "a";
	}

	function addB() {
		$this->thing .= "b";
		return $this;
	}

	function addC() {
		$this->thing .= "c";
		return $this;
	}

	function __tostring() {
		return $this->thing;
	}

}

$obj = new MyClass();
echo $obj->addB()->addC(); //outputs "abc"
echo $obj->addB(); //outputs "ab"
echo $obj->addC(); //outputs "ac"
echo $obj; //outputs "a"

When you initialize the object, the constructor sets the thing property to be a. Each one of the methods returns $this, which of course is the entire object. So if you call addB(), it adds b to the string and then returns $this. So you can chain the addC() method, which is basically calling it on the $this that addB() returned.

I hope this helps you understand method chaining. It took me a little while to figure it out, and explaining it clearly is about as easy as reading this probably is.

I was working on a project recently that required unique API keys to be generated for clients connecting to the server. For various reasons, I settled on the style of license key you commonly see for software packages. You know, the kind you always had to read off the back of a CD case and type in when installing the application. Like H8OV7-HNTB5-JLLOH-W8FG2.

It’s fairly easy to write such a function. The basic idea is to loop around four times—once for each segment—and have a nested loop that runs five times, picking a random character each time. Here’s what I came up with:

function generate_key_string() {

	$tokens = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
	$segment_chars = 5;
	$num_segments = 4;
	$key_string = '';

	for ($i = 0; $i < $num_segments; $i++) {

		$segment = '';

		for ($j = 0; $j < $segment_chars; $j++) {
    			$segment .= $tokens[rand(0, 35)];
		}

		$key_string .= $segment;

		if ($i < ($num_segments - 1)) {
    			$key_string .= '-';
		}

	}

	return $key_string;

}

The $tokens string contains the characters that are valid in the key, so the loop can pick from it. The $segment_chars and $num_segments variables are the number of characters in a segment and the number of segments in the key, respectively. $key_string is an empty string that the loop will add the characters into.

The first for loop runs four times, assuming the desired result is four segments in the key. The inner loop picks a character out of $tokens at random each time it goes around. (PHP strings are also arrays, with the each character having its own numerical offset.) The characters are tacked onto the $segment string.

Then the segment is joined with the $key_string, and a dash character is applied if the loop isn’t on the final segment yet. End result: something like H8OV7-HNTB5-JLLOH-W8FG2.

Now how can you make sure the key is unique when it’s generated?

do {
	$key_string = generate_key_string();
	$result = $db->query("SELECT license_key FROM my_license_key_table WHERE license_key = '$key_string'");
	//$db is a PDO object. If you're not familiar with PDO, check out http://www.webmaster-source.com/2011/08/05/getting-your-feet-wet-with-pdo-and-migrating-old-mysql-code/
} while ($result != false);

You generate a new key string with the function, check to see if it exists in your database, and lather/rinse/repeat until that is no longer the case. Usually you won’t have collisions too often, so it will only need to run once. I’m too lazy to figure out the probability, but considering there are 52,521,875 possible combinations for one 5-character segment…you’re probably not going to run into performance issues anytime soon. And if you do, just add another segment onto your key strings.

There’s a lot of outdated information on the Web that leads new PHP users astray, propagating bad practices and bad code. This must stop. PHP: The Right Way is an easy-to-read, quick reference for PHP best practices, accepted coding standards, and links to authoritative tutorials around the Web.

PHP: The Right Way is a useful guide to how to write PHP that won’t make other developers cringe in horror. It starts off with some tips on how to manage your development environment and then gets to the good part: what not to do. Advice is featured on matters such as database access, password hashing, and other security issues.

The site is an excellent central resource that gives a good overview of things that every beginning PHP developer should be aware of.