Hello Andrew, you can easily implement this function run time. It is not very flexible and far away from what ifsetor was meant to be. Thus I do not think it is a good idea. See comments below.
marcus Tuesday, September 11, 2007, 12:12:55 AM, you wrote: > Here's a patch against HEAD that implements the array_get function > previously suggested on this list. I also attached a test suite, > which should go in ext/standard/tests/array/array_get.phpt. Feedback > is welcome. > Independently, someone else had posted the same idea as a feature > request for PHP 5, and if there's interest I can backport it. > 40792 Open Wish: Function array_get(&$mixed, $key, $defaultvalue) > /* Prototype: > * mixed array_get ( array $search, mixed $key, mixed $default ); array should not be passed as reference as that would be a slowdown unless the function is supposed to create the index key which according to the specs below it doesn't. > * Description: > * Returns the value corresponding to the given key if the key exists > * in the array. $key can be any value possible for an array index. > * If the key does not exist, the function returns $default, or FALSE > * if $default is not specified. Also works on objects. > * Similar semantics to array_key_exists. > */ > Here is the original proposal: > ======= > array_get, a more palatable alternative to ifsetor Things this cannot do but ifsetor can. - Check whether the array exists - Mulitlevel queries - Other types of queries (e.g. object members) - In theory we could have ifsetor even return a writeable reference where a non existing key would either be created or (pretty bad imo) a reference to the default value gets returned. > MOTIVATION > There is an unmet need for an accessor that doesn't generate an > E_NOTICE when the value is missing, as shown by ongoing discussions > and repeated requests for an ifsetor operator. However, ifsetor had a > special-case syntax and generally didn't fit very well with the rest > of the language. > http://devzone.zend.com/node/view/id/1481#Heading2 has a brief > summary. See the Related Functions and Proposals section for more. > Reading over those ideas (firstset(), coalesce(), :?, ifset(), and a > workaround using settype()), most of the best uses boil down to > retrieving values from arrays. > PROPOSAL > As a simpler alternative to constructs such as this common double > array reference... > > $value = isset($_POST['command']) ? $_POST['command'] : ''; > > I propose an array_get function, like this... > > $value = array_get($_POST, 'command', ''); > > The third argument provides a default. This function would require no > special syntax, and makes a very common construct easier to read and > less error-prone to type. It's a concise way of saying that missing > values can be handled gracefully. > Though request processing was used as an example, the function has > wide applicability across many other uses of associative arrays. > > GREAT, BUT WHY NOT ADD IT TO AN INCLUDE FILE, INSTEAD OF THE CORE? > One of the goals is to make everyday PHP code simpler and clearer. > Writers of sample code snippets should be able to rely on array_get() > being available. Otherwise, they will not use it. Clearer sample code > particularly benefits beginners, who would probably find array_get > easier to understand, but anyone else who has to read or maintain > other people's code would benefit from its wide deployment in core as > well. The function is generally useful enough to be part of the > language, and the implementation in C is also more efficient than a > PHP version. > That said, a compatibility function for older versions of PHP is > given below. > SEMANTICS > mixed array_get(array $array, mixed $key[, mixed $default = FALSE]); > > If $array contains the key $key, $array[$key] is returned. Otherwise > $default is returned. > > If $default is not specified, it defaults to FALSE. (NULL would also > be possible, and would more closely match other languages such as > Python with its dict.get method, but other PHP functions tend to > return FALSE to indicate no value.) > > The semantics match > > array_key_exists($key, $array) ? $array[$key] : $default > > ... but for comparison, > > isset($array[$key]) ? $array[$key] : $default > > is subtly different. The preferred array_key_exists version has these > differences: > 1. If $array[$key] exists but has been set to null, that null > value will be returned instead of $default. This is likely to be the > least surprising thing to do. > 2. If $array itself is unset, an error is generated. This is good. > The intention is to gracefully handle a missing $key. But if even > $array itself doesn't exist, there may be another problem, such as > misspelling the array variable. isset() ignores all errors, sweeping > more under the rug than we typically want. > IMPLEMENTATION > A core C implementation of array_get() benchmarked between two and > three times as fast as the implementation in PHP. I'll attach the > patch after responding to feedback. > See the last section for the code of the PHP implementation. > RELATED FUNCTIONS AND PROPOSALS > This function is different than the array_get function proposed and > rejected in http://bugs.php.net/bug.php?id=28185. That function had > no default value and throws a notice when the key doesn't exist, > eliminating the major purpose of this function. > The ?: operator doesn't serve the same purpose, because it causes an > E_NOTICE for missing values. However, ?: and array_get can be used > together to provide short-circuit evaluation, overcoming the > limitations of both. See the LIMITATIONS section for an example. > ifsetor: as discussed above, ifsetor wasn't a regular function. It > required special language syntax support because it attempted to test > whether a direct parameter itself was set or unset, and was > ultimately rejected. > ifset: a related proposal to ifsetor, with a simpler syntax, ifset > was missing a way to control the default value. > See here for more discussion about the 'E_STRICT ternary pain-in-the- > ass expression' and alternatives: > http://keithdevens.com/weblog/archive/2005/Nov/24 > http://www.php.net/~derick/meeting-notes.html#id39 > http://devzone.zend.com/node/view/id/1481#Heading2 > > LIMITATIONS > This proposal doesn't address every requested feature. The third > parameter is always evaluated, so calling a slow function there would > be undesirable. However, the limitation appears to be unavoidable > without special language support, and there are workarounds. These > snippets have approximately equal meanings (though they may differ is > the handling of array values that convert to false): > array_get($_GET, 'foo', slowDefaultCalculation()) > $val = array_get($_GET, 'foo'); if (!$val) $val = > slowDefaultCalculation(); > array_get($_GET, 'foo') ?: slowDefaultCalculation() > The last example uses the new PHP 6 ?: operator. > This function applies only to array elements. Unlike other proposed > functions, it doesn't also attempt to determine whether variables are > set. However, the practical uses suggested for the other functions > generally ended up applying to array elements. > COMPATIBILITY FUNCTION FOR OLDER VERSIONS OF PHP > if (!function_exists('array_get')) { > function array_get($arr, $key, $default = false) { > if (array_key_exists($key, $arr)) { > return $arr[$key]; > } > else { > return $default; > } > } > } > (This version turned in the fastest times out of several variants. > Passing $arr by reference or attempting to return the result by > reference had a huge negative impact, and using the ternary ? : > operator instead of the if/else was slightly slower.) > ======= > -- > Andrew Shearer > http://ashearer.com/ Best regards, Marcus -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
