Tag Archives: Software engineering

PHP Strings Don’t Need Quotes

I bet you didn’t know that PHP strings don’t need quotes! Indeed PHP developers work with strings with either single or double quotes, but actually in some cases you don’t need them.

PHP by Book

Here’s how PHP developer declare a string, which is something very common in any programming language.

$my_var = 'hello world';
// or
$my_var = "hello world";

PHP Tricks

What if you do the following:

echo hello;

That appears to be correct … Well, it’s not absolutely correct. You’ll be “noticed”.

// Notice: Use of undefined constant hello
echo hello;

However if you disable error reporting, the code will be completely fine.

error_reporting(0);
 
// no problem now
echo hello;

Variations

What follows from the thing above is that you can use strings without quotes:

// hello
echo hello;
 
// hello world (concatenated)
echo hello . ' world';
 
// helloworld
echo hello . world;

However you can’t have spaces and most of the “special” symbols.

// syntax error
echo hello world;
 
// syntax error
echo hello!;

Final Words

Although you can do this in PHP, that is completely wrong. The code becomes more difficult to read and understand. In the second place you can miss a $ sign in front of a variable declaration and thus the PHP interpreter will assume this is a string. So disable error reporting isn’t so great sometimes.

JavaScript Performance: for vs. while

JavaScript Loops

If you have read some preformance tests on JavaScript loops, you may have heard that “while” is faster than “for”. However the question is how faster is “while”? Here are some results, but first let’s take a look on the JavaScript code.

The for experiment

console.time('for');
for (var i = 0; i < 10000000; i++) {
	i / 2;
}
console.timeEnd('for');

The while experiment

console.time('while');
var i = 0;
while (i++ < 10000000) {
	i / 2;
}
console.timeEnd('while');

Note – these tests are performed and measured with Firebug on Firefox.

Results

It’s a fact, that you’ll get different results as many times as you run this snippet. It depends also on the enviroment and software/hardware specs. That is why I performed them 10 times and then I took the average value. Here are the values of my performance tests. Note that both for and while perform 10,000,000 iterations.

And the Winner Is

While is the winner with an average result of 83.5 milliseconds, while “for” result is 88 average milliseconds.

As the diagram bellow shows, the while loop is slightly faster. However we should be aware that these performance gains are significant for large number of iterations!

JavaScript Performance: for vs. while
JavaScript Performance: for vs. while

Object Cloning and Passing by Reference in PHP

In PHP everything’s a reference! I’ve heard it so many times in my practice. No, these words are too strong! Let’s see some examples.

Passing by reference in PHP can be tricky!
Some developers think that everything's passed by reference in PHP.

Passing Parameters by Reference

Clearly when we pass parameters to a function it’s not by reference. How to check this? Well, like this.

function f($param)
{
	$param++;
}
 
$a = 5;
f($a);
 
echo $a;

Now the value of $a equals 5. If it were passed by reference, it would be 6. With a little change of the code we can get it.

function f(&$param)
{
	$param++;
}
 
$a = 5;
f($a);
 
echo $a;

Now the variable’s value is 6.

So far, so good. Now what about copying objects?
Continue reading Object Cloning and Passing by Reference in PHP

Does JavaScript undefined Equals undefined?

Weird JS

Does "undefined" equals "undefined"?
Does JavaScript "undefined" equals "undefined"?

As you know sometimes JavaScript can be weird. Let’s see the following example and let’s try to answer the question: does “undefined” equals “undefined”. What do I mean?

First take a look at the following code.

var a;
var b = undefined;
 
// alerts "false"
alert(b == a);

Both a and b are undefined, but they are NOT equal. Now let’s see where it can become a problem.

We have an object with one member variable that is not defined.

var f1 = function()
{
	this.myvar;
};
 
var obj1 = new f1();

Now you’d like to know whether the object “b” has the property “myvar”. There are lots of examples online, but what’s the right way?
Continue reading Does JavaScript undefined Equals undefined?

Some Notes on the Object-oriented Model of PHP

PHP 5 introduces interfaces and abstract classes. To become a little clearer, let us see their definitions.

Interfaces

Object interfaces allow you to create code which specifies which methods a class must implement, without having to define how these methods are handled.
Interfaces are defined using the interface keyword, in the same way as a standard class, but without any of the methods having their contents defined.
All methods declared in an interface must be public, this is the nature of an interface.

To implement an interface, the implements operator is used. All methods in the interface must be implemented within a class; failure to do so will result in a fatal error. Classes may implement more than one interface if desired by separating each interface with a comma.

Abstract Classes

PHP 5 introduces abstract classes and methods. Classes defined as abstract may not be instantiated, and any class that contains at least one abstract method must also be abstract. Methods defined as abstract simply declare the method’s signature – they cannot define the implementation.

When inheriting from an abstract class, all methods marked abstract in the parent’s class declaration must be defined by the child; additionally, these methods must be defined with the same (or a less restricted) visibility. For example, if the abstract method is defined as protected, the function implementation must be defined as either protected or public, but not private. Furthermore the signatures of the methods must match, i.e. the type hints and the number of required arguments must be the same. This also applies to constructors as of PHP 5.4. Before 5.4 constructor signatures could differ.

Some Cases

Now let’s do a quick experiment. According to the definition of interfaces we can define an interface and than an abstract class can implement this interface.
Continue reading Some Notes on the Object-oriented Model of PHP