Arrow, Arrow, who's got the arrow?

[metazai]

Ok, I've made several PHP-enabled sites, and done what I think is some pretty snazzy programming. I know, of course, that compared to professionals, most of it is simple and clumsy, but I'd like to think that I have learned something about PHP. I've taught myself, however, which leaves some startling gaps in my knowledge. I'm about to undertake a monumental task in PHP, and in reading samples of similar applications to what I want to build, I'm running into a question that is so completely pathetic that I could only post it in a forum on a site with the word "Newbie" in the title:

What's with the arrow? I'm having trouble figuring out the exact use of something like this:

$this->inv_table."some text"

It's the little -> that gets me.

Can someone explain what it's for, so I can use it, or at least understand it?

Use small words. I'm obviously a little brain-difisshigntaskdjf4*$*%(&

[sde]

first of all, no need for the 'pathetic question' setup =) .. it's a great question.

-> in php is how you access functions or variables of an object. in your example, this would be the object.

you only use the keyword this when you are accessing properties of a class that you are currently coding in.

i wrote this article a while back. it's just a little introduction to object oriented (OO) programming with php.

Lots of things have changed with OO programming and PHP with PHP5. keep in mind that the link above was written for php4, so it may not be proper PHP5 as far as the style of a class goes.

to answer your question exactly, you are just concatinating aclass varaible with "some_text". the dot in PHP just glues strings together.

it would be the same thing as this:

PHP Code:

<?
$inv_table = "<table border=1><tr><td>";
$end_table = "</td></tr></table>";

echo $inv_table."some text".$end_table;
?>

Other languages such as Java and Javascript are a little different to PHP in this case. They use a + to concatinate ( where php uses a dot ) .. also they use a dot to access a class property ( where php uses -> )

if it was a class, it might look something like this:

PHP Code:

<?
class MyClass(){
  $this->inv_table = "<table border=1><tr><td>";
  $this->end_table = "</td></tr></table>";

  function printTextInTable($some_text){
    echo $this->inv_table . $some_text . $end_table;
  }

  // this is an example of calling a function
  // within the class with this->
  function printWelcome(){
    $this->printTextinTable("Welcome");
  }
}

// now i can use my class to make tables with text
$mc = new MyClass();

// now call the function inside the class.. except this time
// we will be using $mc instead of $this since we are outside the class
$mc->printTextInTable("this will print inside an html table");
?>

probably not the best examples, but feel free to ask more questions if you don't understand.

[metazai]

Cool. I think I . . . almost get it. I don't feel so bad not know what it was now that I know it was OOP, which I'd understood was a method of coding PHP but not one I've used, not coming from a java/C/coder background. Be forewarned you will be seeing further questions on this board from me in the coming weeks.

One question now from the brief but hightly informative article you wrote . . . in the function "article", you have

  function article($id) 
  { 
    $result=mysql_query("select * from articles where id='" . $id . "'"); 
     
    // when defining variables that belong to this class, while inside the class, 
    // use 'this->' before the variable name. 
    $this->id = $id; 
    $this->headline = mysql_result($result,0,"headline");

I'm assuming that $this->headline would get the result from the matching id query, so you could spell that line out like so:

"$this->headline is a class variable that is equal to the data marked "headline" which was pulled from the proper id tag in the query"

But what's the ",0," in the middle for?

Also, unless you don't think it belongs here, using the same example how would you pull an array? Or is that what the "0" indicates?

[sde]

that was written a long time ago .. i should update it as my coding style has changed a lot since then .. the 0 indicates the first record of the rows that are returned in the mysql query when using the mysql_result function.

it wold be the same as saying

PHP Code:

<?
if($row = mysql_fetch_assoc($result)){
  $this->headline = $row['headline'];
}
?>