trace back where original exception came from?

[adrive]

Hi, i'm wondering if it's possible to trace back where an exception had originated from regardless of the level of calls.

In my example, i had to throw each instance of exception as it climbs till level 1.

But the messages are messy, perhaps there's a way to customize these? Calling $e->getLine and $e->getFile at level1 will not return level3.php but level2.php which isn't what i wanted.

(call from level1)

level1.php :

<?php
require_once('level2.php');

try {
	level2();

}
catch (Exception $e) {
	echo $e->getMessage();
}

?>

level2.php :

<?php
require_once('level3.php');
function level2(){
	try {


	level3();

} 
catch (Exception $e) {
	throw new Exception($e);
}
}
?>

level3.php

<?php
function level3(){
	try {

	throw new Exception("..shouting from level 3!!");

} 
catch (Exception $e) {
	throw new Exception($e);
}
}
?>

[laserlight]

Why do you want to know at which line was the exception thrown? I would be interested in knowing what type of exception it was so that I could handle it appropriately.

If you are trying to implement checks for programming errors, use assertions instead.

[adrive]

Not that im checking for programming errors,
but sometimes in a program a certain function might be buried deep inside the framework and would need to go through multiple levels of function calls. And that it might throw an exception.

[laserlight]

Not that im checking for programming errors,
but sometimes in a program a certain function might be buried deep inside the framework and would need to go through multiple levels of function calls. And that it might throw an exception.

What you want to do is to change:

function level2(){
	try {


	level3();

}
catch (Exception $e) {
	throw new Exception($e);
}
}

to:

function level2() {
    level3();
}

In other words, instead of translating the exception (and in fact you do not translate it at all since you rethrow an exception of the same type), let it propagate. This is the correct thing to do if you are unable to handle the exception at that level or translate it to a more appropriate type of exception.

Likewise, it is pointless to write:

function level3(){
	try {

	throw new Exception("..shouting from level 3!!");

}
catch (Exception $e) {
	throw new Exception($e);
}
}

You should write:

function level3() {
    throw new Exception("..shouting from level 3!!");
}

[adrive]

shouldn't throw statements always be written in a try and catch block? or i had too much java before this 😃

for example the one you suggested to do level2() like this :

function level2() {
    level3();
}

be written as :

function level2() {
 try{
    level3();
 }
 catch(Exception $e){
   throw $e;
 }
}

this way, at least it's not re-throwing a new exception instance, but propagating it out to higher level to catch.

[laserlight]

shouldn't throw statements always be written in a try and catch block? or i had too much java before this

No, not in both PHP and Java. One valid use for throwing an exception in a catch block would be to translate to a more appropriate exception. Another possible use is to log the error and then rethrow the exception. Otherwise, a try/catch block means that you will handle and not propagate the exception.

this way, at least it's not re-throwing a new exception instance, but propagating it out to higher level to catch.

Total waste of effort when the exception mechanism will propagate the exception without your interference. If you are doing this in Java as well, then it is time to change your Java programming habits too.