What does "->" mean?

[Anon]

I have been learning PHP for a while now, but I have yet to write code that looks anything like this:

$this->subject = $subject;

mainly because I can't figure out, in plain english, what the -> symbol (operator?) does (or means).

I had never programed anything prior to PHP and, despite writing some nifty stuff lately, I just can't figure this out!

Thanks in advance,
Erik

[Anon]

Erik, the string "$this->subject" refers to a variable declared and used within a class. A class is a Object Oriented Programming concept, where you group every relevent variable and function into a single object.

So imaging you write a PHP script to display a table. You have one array storing all the column headers, a second array storing all the row headers, and a third array to store the rest of the table content. You also have a procedure to use all these 3 arrays to construct a table in html.

This is not the best example, but say you have to do alot of these type of tables, you don't want to repeat the same code over and over again. What you do is store this piece of code as a class. Then you can create a instant of this class object everytime you need to output a html table.

the variable "$this" is just a simple way for the class object refer to itself.

the string "->" tells the instance you created, now you are using a variable or function in this class.

the string "subject" is just a variable you have declared in this class. For example, for any of the 3 arrays you can do "$this->array1", "$this->array2" or "$this->array3".

To access a function within the class, its very similar to accessing the class variables. You just do "$this->createHTMLtable()" assuming 'createHTMLtable' is a function you wrote to generate the html table.

Hope this helps.

-Will

[Anon]

Click on the articles section on this site and look for Object Oriented or OOP articles.

-> is used to reference class members and methods. You'll have to read up on this extemely broad subject via articles on this an many other sites.

[Anon]

Thanks, Will. That was very helpful. The next question this raises for me is: what is the major difference between Classes and Functions? I know they are different (I have written plenty of functions) but they also seem very similar.

As Ken mentioned, I need a better understanding of OOP, but what is the benefit of a Class when I can just include a function that generates a table (per your example) and then pass it content and run it whenever I want?

Thanks again,
Erik

[Anon]

Erik, Object Oriented Programming is NOT always better than functional/procedural programming. Don't fall into that trap.

Depending on the way you learned your programming or the natural way you organize logic, either one would work fine.

class is simple a set of variable and function you mentally consider them to be working all together.

Say you have several functions: head(), body(), arm(), leg()..etc. You can naturally assume all these functions will be working together to achieve one goal. Class is a simple way for you to organize these function into a single script.

Class can also be built upon other classes, this is the 'inheritance' nature of class. Say you create a class 'polygon'. You can create a class, say 'square', that has all the abilities(functions) of the polygon class, but with its own extra set of functions.

There is really alot more to class than the set of concept I have described here. Use Ken's link should help.

-Will

[Anon]

I really should read up on this stuff. I find I am rewriting a lot of core code "snippets" and functions on different projects when I could just write a class that does something useful (like generating a table from an array or a body from severed limbs) and reuse it forever.

Thanks!