Category Archives: micro tutorial

Construct a Sorted PHP Linked List

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This is really a draft, but I somehow decided to post it. Here’s a simple linked list in PHP, where only the add() method is slightly different. When you have an item to add it’s placed on the “right” place – the result is a sorted list.

Few notes before the code! This list is designed for integers, but I plan to “extend” it somehow and it can be improved a lot. In my future posts I’ll post something more about the complexity of the algorithm and an analysis of it.

class Node
{
    public $data;
    public $next;
    public $prev;
 
    public function __construct($data, $prev, $next)
    {
        $this->data = $data;
        $this->prev = $prev;
        $this->next = $next;
    }
}
 
class LinkedList
{
    protected $front = null;
 
    public function add($data)
    {
        if (!$this->front) {
            $node = new Node($data, null, null);
            $this->front = &$node;
        } else {
            if ($data < $this->front->data) {
                $node = new Node($data, null, $this->front);
                $this->front = $node;
                return;
            }
 
            $current = $this->front;
            while ($current) {
                if ($current->data < $data && isset($current->next) && $current->next->data > $data) {
                    $node = new Node($data, $current, $current->next);
                    $current->next = $node;
                }
                if ($current->data < $data && !isset($current->next)) {
                    $node = new Node($data, $current, $current->next);
                    $current->next = $node;
                }
                $current = $current->next;
            }
        }
    }
 
    public function printl()
    {
        $current = &$this->front;
        while($current) {
            echo $current->data, '<br />';
            $current = $current->next;
        }
    }
}
 
$list = new LinkedList();
$list->add(13);
$list->add(14);
$list->add(15);
$list->add(11);
$list->add(12);
$list->add(17);
$list->add(10);
$list->add(16);
 
$list->printl();

jQuery: Setting Up a Vector Path Fill Color

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It’s quite unusual to think of the jQuery’s attr() method as a generic method that can only change basic attributes as value, style, etc. However attr() can change whatever DOM element attribute. In this case you may know that the SVG path element can have a fill attribute, so you can simply setup a:

$('path').attr('fill', '#ccc');

2xjQuery: Select a Selector

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Selectors in jQuery

jQuery JavaScript Library

If you’re familiar with jQuery you should already know what are selectors and how they work. However we’re used to get some DOM element with a specific selector, but actually sometimes you cannot select directly what you need. This is especially true when mixing more than one JavaScript libraries. In my case OpenLayers generated a vector layer and jQuery was supposed to change the vectors fill-color property.

OpenLayers

With the simple $(‘path’) I easily got all vectors in the current document, but the problem was that I took them as text. Thus it came to me to use nested jQuery – $($(‘selector’));

To describe what actually happened in my case, let me show you a breve example.

Example

Here’s a short HTML markup:

<div><span>text text</span></div>

With jQuery I can select both the DIV and SPAN with the simple $(‘div’) and $(‘span’), but just for the example lets assume I’ve only the inner text of the DIV tag:

$('div').html();

That was the case in the OpenLayers/jQuery problem. Now I can easily use another jQuery selector:

$($('div').html());

This will return the same as $(‘span’) – a jQuery object.

5 PHP String Functions You Need to Know

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Strings in PHP

The Task

First of all what we’d like to achieve? The task is to convert a string, most of the cases single word, by capitalize the first letter. In my case I’ve the world countries names all lower cased, while I need them with first letter capitalized. In example “united states” must become “United States”, but not “United states” or “UNITED STATES”. So here began the journey into PHP string functions, especially those for capitalization!

1. ucwords

The first thing you find in the PHP Manual is the ucwords function. It changes the first letter to a capital letter, but it does not do the job. Why? Well let me show you an example.

$str1 = 'foo bar';
$str2 = 'Foo bar';
$str3 = 'FOO BAR';
$str4 = 'фуу бар';
 
echo ucwords($str1); // Foo Bar
echo ucwords($str2); // Foo Bar
echo ucwords($str3); // FOO BAR
echo ucwords($str4); // фуу бар

Here we have four strings. A lower cased, an upper cased, a mixed cased and … a lower cased Cyrillic string. First of all the main reason why ucwords doesn’t fit here is because of the Cyrillic string. Whatever non-Latin string you have you can forget about capitalization. However the other strings conversions are also interesting. Take a look at the third string! Here the string remains “FOO BAR” instead of going “Foo Bar”, which simply means that this function only looks, and hopefully changes, the first letter.

So here we have two questions. How can we overcome the Cyrillic problem and how to “normalize” the UPPER CASE string?

2. ucfirst

This is another useful function in PHP. ucfirst as you may guess from its name converts a string by only changing its first letter. So “Foo bar” will remain “Foo bar”, while with ucwords it has become “Foo Bar”. Let’s see what this function does:

$str1 = 'foo bar';
$str2 = 'Foo bar';
$str3 = 'FOO BAR';
$str4 = 'фуу бар';
 
echo ucfirst($str1); // Foo bar
echo ucfirst($str2); // Foo bar
echo ucfirst($str3); // FOO BAR
echo ucfirst($str4); // фуу бар

Here even the first string has only one capital letter – “foo bar” became “Foo bar”, and yet again we’ve the Cyrillic string unchanged. It simply doesn’t help us here!

3. mb_convert_case

As a PHP developer you know what the “mb_” prefix means – multibyte. This is quite useful. You can convert the string whatever the encoding is, so perhaps we can overcome the Cyrillic problem. But before proceeding to tests, let’s take a look at the parameters of this function.

The first thing to note here is that mb_convert_case doesn’t contain the case in its name – upper or lower. There’s a second parameter, after the first which is the string itself, who setups that. Note that here you don’t have the typical camel case or capitals parameter name, but MB_CASE_TITLE (as you know in English the title is always capitalized):

echo mb_convert_case($str, MB_CASE_TITLE, ...

And a third one which specifies the encoding:

echo mb_convert_case($str, MB_CASE_TITLE, 'utf-8')

Now let’s see what we can achieve with it:

$str1 = 'foo bar';
$str2 = 'Foo bar';
$str3 = 'FOO BAR';
$str4 = 'фуу бар';
 
echo mb_convert_case($str1, MB_CASE_TITLE, 'utf-8'); // Foo Bar
echo mb_convert_case($str2, MB_CASE_TITLE, 'utf-8'); // Foo Bar
echo mb_convert_case($str3, MB_CASE_TITLE, 'utf-8'); // Foo Bar
echo mb_convert_case($str4, MB_CASE_TITLE, 'utf-8'); // Фуу Бар

As you can see now the Cyrillic problem doesn’t exists and mb_convert_case is intelligent enough to change “FOO BAR” into “Foo Bar” – as I said this is the English style titling. That is by no means the solution when you deal with capitalization with different encoding.

However there is another approach to overcome the all UPPER CASE conversion problem. A possible solution is to convert the string first to a lower case string.

4. strtolower

strtolower is very useful PHP string function and perhaps any PHP developer has used it at least once. But yet again – it does not do the job. Again because of the encoding problem.

echo strtolower('ФУУ БАР'); // #*&amp;$(#*%#

As you can see the Cyrillic string cannot be lower cased! Let’s search again into the “mb_” universe.

5. mb_strtolower

This is the function. Again you’ve to specify the encoding:

echo mb_strtolower('ФУУ БАР', 'utf-8')

Conclusion

It doesn’t matter whether you’re native English speaker or not. Most of the web sites are multilingual and you cannot be sure what happens when you convert strings in Alphabets different from the Latin. Thus be careful even when everything seems to be OK with Latin string tests.

Looping Animation with JavaScript and Raphaël

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Raphael is a popular JavaScript library helping you to manage vectors via SVG or VML in your browser. It is extremely helpful and very easy to learn and use. The interesting thing is that in the browser you can do very powerful things with vectors, but they remain very less known. However with such libraries like Raphael the task is really simple.

Animation

As I said animating some vector properties is as simple as:

var paper = Raphael('canvas', 1024, 500);
var c = paper.circle(50, 50, 6).attr({fill : '#f00'});
c.animate({r : 10, fill : '#00f'}, 1000);

Here we change the radius and the background color of the circle for 1000 milliseconds.

The same thing can be done with any property with any other JavaScript library as jQuery. But as in jQuery, Raphael or whatever library the animation is not looping. That’s natural you can just change a property by animating it, but the looping animation suggests at least two animations. So it’s a developers job to implement this. Here’s a simple way to do this.

Two Way Animation

The solution here is using two functions calling each other.

var paper = Raphael('canvas', 1024, 500);
var c = paper.circle(50, 50, 6).attr({fill : '#f00'});
 
function a() {
    c.animate({r : 10, fill : '#00f'}, 1000, b);
}
function b() {
    c.animate({r : 6, fill : '#f00'}, 1000, a);
}
a();