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SimpleXML's atXPath method

php.internals

Willian Veiga

9 years ago
Hello, What do you think about a new method, called atXPath, that would return a single SimpleXMLElement? Details: https://github.com/php/php-src/pull/1717 https://bugs.php.net/bug.php?id=45201 Thank you, Willian.

Rowan Collins

9 years ago
On 06/01/2017 14:03, Willian Veiga wrote:
> Hello, > > What do you think about a new method, called atXPath, that would return a > single SimpleXMLElement? > > Details: > > https://github.com/php/php-src/pull/1717 > https://bugs.php.net/bug.php?id=45201 > > Thank you, Willian. >
My first thought on this was "what does the 'at' mean?" I see now that it's copied from another library, but "atXPath" really doesn't make me think "xpath for single element". My second thought is that this feature is actually no longer needed. The original feature request was to avoid the need for an intermediate variable when you know you're getting back one result: $firstresult=$xml->xpath('element[@called="XYZ"]'); $secondresult=$firstresult[0]->xpath('child[@named="ABC"]'); $finalresult=$secondresult[0]; But in all versions of PHP since 5.4 you can simply add the [0] on the end of the function call anyway: $finalresult=$xml->xpath('element[@called="XYZ"]')[0]->xpath('child[@named="ABC"]')[0]; Like the original proposal for an extra parameter, this extends to selecting whichever result you want, as long as you're sure it exists. Example: https://3v4l.org/1k9rk If you don't know for sure that there will be enough results, then chaining will give an error either way, and this isn't really any different from any other method that might or might not return the expected object. Regards,
-- Rowan Collins [IMSoP]

Joe Watkins

9 years ago
Evening Rowan, I must protest: It is wasteful, unclear, and generally nasty, to create, return, and manipulate an array if you are only ever going to reference one element in code. It is quite normal to know the structure of a document ahead of time, and this would allow you to write more succinct and less wasteful code. It would appear valuable to me ... I'm not in love with the name of the thing, but the basic idea appears valuable. Cheers Joe On Sat, Jan 7, 2017 at 4:26 PM, Rowan Collins <rowan.collins@gmail.com> wrote:

Kalle Sommer Nielsen

9 years ago
2017-01-07 18:01 GMT+01:00 Joe Watkins <pthreads@pthreads.org>:
> Evening Rowan, > > I must protest: It is wasteful, unclear, and generally nasty, to create, > return, and manipulate an array if you are only ever going to reference one > element in code. > > It is quite normal to know the structure of a document ahead of time, and > this would allow you to write more succinct and less wasteful code. > > It would appear valuable to me ... I'm not in love with the name of the > thing, but the basic idea appears valuable.
I agree, the feature/idea is great. Coming from someone who worked a fair bit with XML recently (I know I know!). Same goes for the method naming, seems a little bit awkward
-- regards, Kalle Sommer Nielsen kalle@php.net

Rowan Collins

9 years ago
On 07/01/2017 17:01, Joe Watkins wrote:
> Evening Rowan, > > I must protest: It is wasteful, unclear, and generally nasty, to > create, return, and manipulate an array if you are only ever going to > reference one element in code.
Meh, feels like a micro-optimisation to me, and "[0] to access first search result" seems pretty obvious, but fair enough if you disagree. I know development's not a zero-sum game, but there are plenty of things I'd add to the SimpleXML extension that aren't just aliases for things you can trivially do already. For instance, sticking with XPath usage, the fact that registerXPathNamespace() only affects the current element, so has to be re-run as you traverse: $sx->registerXPathNamespace('a', 'http://example.com'); $foo = $xml->xpath('//a:foo')[0]; // do something with $foo $foo->registerXPathNamespace('a', 'http://example.com'); // won't work without this $bar = $foo->xpath('./a:bar')[0]; That's a lot more intrusive than needing to add "[0]" next to a few method calls. Regards,
-- Rowan Collins [IMSoP]

Joe Watkins

9 years ago
Evening Roawn, There is no competition to see which single problem we are going to solve, we can fix more than one thing, obviously :) What we are discussing here is the value of this particular feature, not the value of things that nobody has taken the time to propose, implement, or fix. This contributor has waited a year for this conversation to start, it would be nice if we could stay focused. If you would like to talk about the shortcomings in simplexml (or anything), might I suggest you start a new topic and see if you can drum up some support for changes/fixes :) Cheers Joe On Sat, Jan 7, 2017 at 6:24 PM, Rowan Collins <rowan.collins@gmail.com> wrote:

Rowan Collins

9 years ago
On 07/01/2017 19:29, Joe Watkins wrote:
> Evening Roawn, > > There is no competition to see which single problem we are going to > solve, we can fix more than one thing, obviously :) > > What we are discussing here is the value of this particular feature, > not the value of things that nobody has taken the time to propose, > implement, or fix. > > This contributor has waited a year for this conversation to start, it > would be nice if we could stay focused. >
Indeed, I didn't mean to imply otherwise, and sorry if I gave that impression. There is a small cost to adding new methods like this, in future maintenance, and the future consistency of the extension, but you're right that it's not a big deal, and other than finding the right name, I've no real reason to object to this method. Regards,
-- Rowan Collins [IMSoP]

Joe Watkins

9 years ago
Evening Rowan, Thank you. Now we can get to the really hard problem ... naming things :D I'm afraid I have no good suggestions. I can find API's that use the suggested name, but they vary in functionality (some overlap). There's also XmlNode.SelectSingleNode from C#, but sounds pretty horrible to me, variations on it might be: selectPath singlePath singleNode None of them really sound right to me, but may provoke someone else to do better. Over to you, someone else ... Cheers Joe On Sat, Jan 7, 2017 at 11:02 PM, Rowan Collins <rowan.collins@gmail.com> wrote:

Stephen Reay

9 years ago
Hey all, Is there a major issue with simply adding a $limit parameter to the existing xpath() method instead, and stopping searching after that many elements are found? Cheers Stephen Sent from my iPhone

Willian Veiga

9 years ago
We don't have enough opinions to continue. Could anybody else contribute to this discussion? This way, we can decide the future of the PR #1717. Thank you very much, Willian Gustavo Veiga.

Willian Veiga

9 years ago
We don't have enough opinions to continue. Could anybody else contribute to this discussion? This way, we can decide the future of the PR #1717. Thank you very much, Willian Gustavo Veiga.