RE: [PHP] Execution order of PHP

From: Sándor Tamás > 2010.03.10. 14:41 keltezéssel, Bob McConnell írta: >> From: Auke van Slooten >> >>> In a hobby project I'm relying on the order in which the following >>> >> piece >> >>> of PHP code is executed: >>> >>> $client->system->multiCall( >>> $client->methodOne(), >>> $client->methodTwo() >>> ); >>> >>> Currently PHP always resolves $client->system (and executes the __get >>> >> on >> >>> $client) before resolving the arguments to the multiCall() method >>> >> call. >> >>> Is this order something that is specified by PHP and so can be relied >>> upon to stay the same in the future or is it just how it currently >>> >> works. >> >>> If it cannot be relied upon to stay this way, I will have to rewrite >>> >> the >> >>> multiCall method and API... >>> >> Think about it from the parser's point of view. It has to evaluate >> $client->system to determine the parameter list for multiCall(). Then it >> has to evaluate those parameters before it can stuff their values into >> the stack so it can call the function. But, whether it evaluates the >> parameter list left-to-right or vice versa is implementation dependent. >> I don't believe you can rely on it always being the same unless you >> always use the same interpreter. > > I think it cannot be that the evaluation order of the parameters is > implementation dependent. > Just think about it: > $someobject->method($a++, $a++); > > What will be the result? Or there has to be some directive to tell the > parser to evaluate the parameters from left to right or vice versa. > And if there isn't, in some future release, there has to be. The result of that line would be undefined in any language I am familiar with. I could manually implement a variation in assembler that would be safe, but nowhere else. You have too many operations in a row on a single variable without adequate checkpoints between them. Bob McConnell