Do all variables in methods need to be object properties? (PHP) - php

Question

I'm learning OO PHP and am trying to get some of the coding practices straight. Here is a pared down version of some code I'm using for error (and exception) handling:
final class MyErrorExceptionHandler {
private $level = array(); // error levels to be handled as standard errors
private $path = array(); // full path to file
private $path_short; // filename plus working dir
public function myErrorHandler($severity, $message, $file, $line) {
if (error_reporting() & $severity) { // error code is included in error_reporting
$this->level = array(E_WARNING => 'warning',
E_NOTICE => 'notice',
E_USER_WARNING => 'user warning',
E_USER_NOTICE => 'user notice');
if (array_key_exists($severity, $this->level)) { // handle as standard error
/*$this->severity = $severity;
$this->message = $message;
$this->file = $file;
$this->line = $line;*/
$this->printMessage($severity, $message, $file, $line);
} else { // fatal: E_USER_ERROR or E_RECOVERABLE_ERROR use php's ErrorException converter
throw new ErrorException($message, 0, $severity, $file, $line);
}
}
} // fn myErrorHandler
private function printMessage($severity, $message, $file, $line) {
echo ucfirst($this->level[$severity]) . ': ' . $message;
$this->shortenPath($file);
echo ' in ' . $this->path_short . ' on line ' . $line;
} // fn printMessage
private function shortenPath($file) {
$this->path_short = $file;
$this->path = explode(DIRECTORY_SEPARATOR, $file);
if (count($this->path) > 2) { // shorten path to one dir, if more than one dir
$this->path_short = array_pop($this->path); // filename
$this->path_short = end($this->path) . DIRECTORY_SEPARATOR . $this->path_short; // dir+file
}
} // fn shortenPath
} // cl MyErrorExceptionHandler
The title of this question is probably a little bit off because I'm not 100% on the terminology. Basically I'm trying to figure out a few things.
Is it right to explicitly declare $level and $path as arrays?
Should $level be declared as it is (and made $this->level)? If so, have I assigned its value (E_WARNING etc.) in a wise place? Would the constructor (not shown here) be a smarter choice?
Note the commented block in myErrorHandler(). Originally I had declared all of these properties at the top of the class, and then called $this->printMessage() without any parameters. Which is the more correct way? If I keep the code as is, would I want to then use $this->severity = $severity etc. inside printMessage()?
So, would it be better to:
replace
$this->shortenPath($file);
echo ' in ' . $this->path_short . ' on line ' . $line;
with
$path_short = $this->shortenPath($file);
echo ' in ' . $path_short . ' on line ' . $line;
ultimately, and give a return value in shortenPath()?
I realize this is a mishmash of several different questions, but what I'm trying to get at is a common inquiry about the proper style of declaring/using variables/properties, specifically when dealing with methods.
To summarize: When should I use $this->foo = $foo?

Answer 1

EDIT: sorry, I have assumed below that you would create a new instance of the 'object' with each error which obviously you are not doing. Just edited my answer to reflect this.
"When should I use $this->foo = $foo?"
There can be several cases in which you would do this, but it's usually if you create $foo within a method and wish to have that then accessed by the entire object.
For example, if you wanted to call on an object and use that within this particular object (if it doesn't make sense to extend). You would do something like:
$foo = new DataModel();
$this->foo = $foo;
OR
$this->foo = new DataModel();
That object may be a decorator or something else related to error handling and the above code would usually feature in your constructor. You could then access the methods of that object any time by using:
$this->foo->objectMethod();
..and to express something noted in the comments to this answer:
"would you assign $file to the object as that is used in several methods?"
I wouldn't assign $file to the object,
here's why. The semantics of the word
"property" means "belongs to". In your
case, your class is a error handler.
$file doesn't belong to the error
handler, it belongs to an error
instance. If your class was
MyErrorHandler_Error (created for each
instance of a triggered error), then
$file would be a property of that
class, along with $line and $level.
To answer what I can from your other questions:
It's neither. I would consider it preference.
Yes - any variables or values which should be available to your entire object and required for the object to run properly, should probably be set within your constructor, if not within your variable declarations (not sure of terminology there) at the top of the class.
read the comments below. Because this particular class deals with multiple instances of errors - assigning the properties of those errors to the object wouldn't be best practice as you will be overwriting them with each new error. However, it does make sense to store all of your errors and error properties within an array assigned to the object if you require to access historical data. For example, at the moment, if you create a new error - that is all you are doing. You have no way of accessing any old errors this object has created.
see above
You should also think about conflicts when assigning properties to objects. Are you likely to reassign, because if so, the old property will be gone. Fairly simple but still something you have to consider.