Classes not properly included

binaryexp

I came accross something interesting the other day involving extended classes which have the parent class included as a file.

//parent.php
class data 
{
}

//child.php
include ("parent.php");
$somthing = new extdata();

class extdata extends data
{
}

Now if child.php is executed it returns an error that it cannot find the extdata class! However if the parent.php code is put directly into child.php (so without using an include statement) then everything is fine.

So, does anyone know why this is?? It's the same result with php4 and php5.

eoghain

I've found many problems when including files. Mainly is has to do with the location of those files in regard to the location of the executing script.

So if you had an include directory (/includes) and above that was your executing index.php. To get a file from the include directory into index.php you would use this:

include "includes/inc_file.php";

. But if your inc_file.php wanted to include inc_file2.php then you'd get the problem that you are describing.

So you need to do one of these to fix your problem:

Have all ofyour files inlcuded in your executing script.
Have your include directory included in the search path (in php.ini).
Use full paths in your include statements.
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There are probably other fixes but these are the ones that come to the top of my head.

Sgarissta

put

 $something = new extdata();

AFTER you define the extdata class.

binaryexp

Thanks for the response, but I'm not sure that either really helps me. Firstly eoghain:
You suggested 3 fixes,

Have all of your files inlcuded in your executing script.

Have your include directory included in the search path (in php.ini).

Use full paths in your include statements.
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The first suggestion obviously works but is not very useful, the second two seem to make no difference - the error is the same. I don't think that the location of the scripts makes any difference, as long as the include line is correct it should not matter whether it is a full path or not should it?

To Sgarissta: that is a solution but again it's not too elegant as I'm sure you will agree it's nice to have includes first, then some code, and then the classes.

But really I still don't know why PHP acts in this way. Shouldn't includes work properly, or is this part of some security feature??

laserlight

In PHP4 functions do not have to be defined before they are used, so long as they are defined, unless they are defined conditionally.
I presume the same applies for classes, but then it is best if you explicitly define before use.

My suggestion would be something along the lines of:

//parent.php
class data
{
}

//child.php
require_once "parent.php";

class extdata extends data
{
}

//implementation.php
require_once "child.php";

$something = new extdata;

binaryexp

I like your solution laserlight. I suppose that would enable me to keep all the classes in separate files.

In PHP4 functions do not have to be defined before they are used, so long as they are defined, unless they are defined conditionally.
I presume the same applies for classes, but then it is best if you explicitly define before use.

So what exactly counts as a definition? I don't see why in my original example everything isn't well defined.

eoghain

binaryexp, maybe I wasn't clear in my explanation so lets see if this clears it up.

When you run a script (index.php) that is in your WebRoot (/usr/local/apache/htdocs) and it includes a class that is in an includes folder under your WebRoot (/usr/local/apache/htdocs/includes) you need to specify in the include line where to find that class:

<?php
// My index.php
include "includes/MyClass.php";
?>

That is all well and good the script that is currently running (index.php) knows that it has to look in a directory called includes that exists in it's current directory or in the search path defined in php.ini.

Now if your included class (MyClass.php) needs to include another class that exists in it's same directory (/usr/local/apache/htdocs/includes) you'd think that you could just name it. Unfortunatly that isn't correct since the script that is running will think that that include is in it's own directory. So you have to take that into consideration.

Here is what PHP sees as it's processing things:

// Main index.php script located in /usr/local/apache/htdocs
<?php
include "includes/MyClass.php";
?>

// MyClass.php script located in /usr/local/apache/htdocs/includes
<?php
include "AnotherClass.php";
?>

// As PHP Processes index.php this is what it does
<?php
inlcude "includes/MyClass.php";
?>

/*
Process include line (this replaces the include line with the file that is being included
*/
<?php
// include "includes/MyClass.php";  -- Replaced by lines below by PHP
<?php
include "AnotherClass.php";
?>
?>

/*
At this point PHP is still in the /usr/local/apache/htdocs directory, and when it trys to include AnotherClass.php it doesn't know where to find it.
*/

I hope this explination was more informative.

binaryexp

Ok eoghain, I understand what you mean now. That may actually be quite useful information for the future, however I don't see how it applies to this particular problem. Since there is only one include file changing the path will not help.

Thanks for the info though.