In PHP, how do variable scope rules apply to Try/Catch blocks? Do variables declared within the try
block go out of scope when the block has finished? Or are they in scope until the end of the function/method?
For example:
try { // This may throw an exception when created! $o = new Pronk(); } catch (Exception $ex) { // Handle & exit somehow; not important here return false; } $o->doPronk();
Is this valid? Or should $o = NULL;
be set before the try/catch to keep $o
in scope?
(I know that the sample code does work, however I also know PHP can get a little stupid when it comes to scoping. My question is, ideally, how should it work? What is the correct and proper way to do this?)
So, if you declare a variable in try block, (for that matter in any block) it will be local to that particular block, the life time of the variable expires after the execution of the block. Therefore, you cannot access any variable declared in a block, outside it.
Variables declared within the try/catch block are not in scope in the containing block, for the same reason that all other variable declarations are local to the scope in which they occur: That's how the specification defines it. :-) (More below, including a reply to your comment.)
The primary method of handling exceptions in PHP is the try-catch. In a nutshell, the try-catch is a code block that can be used to deal with thrown exceptions without interrupting program execution. In other words, you can "try" to execute a block of code, and "catch" any PHP exceptions that are thrown.
I actually don't think there's anything inherently wrong about nested Try / Catch blocks, except that they can be difficult to navigate and are likely a sign that you could do some refactoring (the inner Try / Catch into its own method, for example).
Your code is valid. Variable scope in PHP is by function, not block. So you can assign a variable inside the try
block, and access it outside, so long as they're in the same function.
I believe this is opinion based mostly. The code is correct and it will work as expected as long as the catch
block always has the return
statement. if the catch
block does not return, the flow will continue and the code outside the try/catch block will be executed, and it will fail, because $o
won't be initialized. You will be able to access $o
because of the lack of block scope in php, but the method won't exist because the object construction failed.
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