I have an array and want to fill the some items depend on previous item's values:
$order = array(
'items_price' => 200,
'tax_price' => 18,
'total_price' => function () {
return $order.items_price + $order.tax_price;
})
How can I do that?
Well, that actually is doable. You cannot reference values in the array from within the array itself; but if you declare variable references for the needed array values, you can pass those references to the closure (function) using use :
$order = array(
'items_price' => ($ip = 200),
'tax_price' => ($tp = 18),
'total_price' => function() use ($ip, $tp) {
return $ip + $tp;
}
);
echo $order['total_price']();
That echoes out 218 ..! But the downside is that the passed references / params are static. Try
$order['items_price'] = 100;
echo $order['total_price']();
The result are a disappointing 218 ... Even though items_price actually are changed to 100, the params passed to total_price are the same as when the array were created. They are not magically updated, the array are not a piece of dynamic code, it is a data structure.
It was a very interesting question indeed, but I do not see any practically use. It seems to me you in this case should use classes instead of arrays.
Related
function values($id,$col)
{
$vals = [1=>['name'=>'Lifting Heavy Boxes']];
return $vals[$id][$col];
}
$complete = [1=>["id"=>"2","sid"=>"35","material_completed"=>"1","date"=>"2017-12-18"]];
$form = 'my_form';
array_walk($complete, function(&$d,$k) use($form) {
$k = values($k, 'name').' ['.date('m/d/y',strtotime($d['date'])).'] ('.$form.')';
echo 'in walk '.$k."\n";
});
print_r($complete);
the echo outputs:
in walk Lifting Heavy Boxes [12/18/17] (my_form)
the print_r outputs:
Array
(
[1] => Array
(
[id] => 2
[sid] => 35
[material_completed] => 1
[date] => 2017-12-18
)
)
I have another array walk that is very similar that is doing just fine. The only difference I can perceive between them is in the one that's working, the value $d is already a string before it goes through the walk, whereas in the one that's not working, $d is an array that is converted to a string inside the walk (successfully, but ultimately unsuccessfully).
Something I'm missing?
And here's the fixed version:
array_walk($complete, function(&$d,$k) use($form) {
$d = values($k, 'name').' ['.date('m/d/y',strtotime($d['date'])).'] ('.$form.')';
});
That's what I was trying to do anyway. I wasn't trying to change the key. I was under the mistaken impression that to change the value you had to set the key to the new value.
You cannot change the key of the array inside the callback of array_walk():
Only the values of the array may potentially be changed; its structure cannot be altered, i.e., the programmer cannot add, unset or reorder elements. If the callback does not respect this requirement, the behavior of this function is undefined, and unpredictable.
This is also mentioned in the first comment:
It's worth nothing that array_walk can not be used to change keys in the array.
The function may be defined as (&$value, $key) but not (&$value, &$key).
Even though PHP does not complain/warn, it does not modify the key.
I have an array consisting of 4 fields.
$retval[] = array(
"name" => "$dir$entry/",
"type" => filetype("$dir$entry"),
"size" => 0,
"lastmod" => filemtime("$dir$entry")
);
I want to sort this array depending on a variable, which contains either 1 of the 4 field (eg: type, name etc)
$sortBy = $_GET['sortBy'];
This function should use the $sortBy variable:
function compare_field($a, $b){
return strnatcmp($a["'.$sortBy.'"], $b["'.$sortBy.'"])
}
And is called like this:
usort($retval, "compare_field");
But the construction doesn't work ..
Hope someone can point me in the right direction, being the obvious newby I am.
First, you're sorting by a key that is actually: '..', not the value of $sortBy. You're trying to use a variables value as the key, to do that, you don't need to mess around with quotes, just write $arrayName[$keyVariable]. That's it.
Second is that compare_field had no access to the $sortBy variable. That variable is local to the scope where it was created, or it's a global variable. Either way, functions don't have access to it.
If you want the usort callback to have access to the $sortBy variable, the easiest way would be to use a closure (anonymous function) as callback:
usort($retval, function ($a, $b) use ($sortBy) {
return strnatcmp($a[$sortBy], $b[$sortBy]);
});
I have an Eventbus that takes a filter name as its first parameter and a Closure as second parameter. Like this:
$this->EventBus->subscribe('FilterTestEvent', function(){/*Do Something*/});
It's called like this:
$filteredValue = $this->EventBus->filter('FilterTestEvent', $anyValue);
What I want now is to pass an array as reference to the Closure that then is changed in any way (here: add elements) and then return something as the filtered value:
$item_to_change = array('e1' => 'v1', 'e2' => 'v2');
$this->EventBus->subscribe('FilterTestEvent', function(&$item){
$item['new'] = 'LoremIpsum';
return true;
});
$filtered = $this->EventBus->filter('FilterTestEvent', $item_to_change);
Now I would a print_r($item_to_change) expect to look like the following:
Array
(
[e1] => v1
[e2] => v2
[new] => LoremIpsum
)
But instead it looks like the original array:
Array
(
[e1] => v1
[e2] => v2
)
The eventbus internally stores all closures and calls them if needed through call_user_func_array() with the closure as first argument and the value as the only argument array element.
How can I achieve what it's meant to do?
Source Code to the Eventbus: http://goo.gl/LAAO7B
Probably this line:
$filtered = $this->EventBus->filter('FilterTestEvent', $item_to_change);
is supposed to return a new filtered array, not modify the original one.
So check it:
print_r($filtered);
Passing by reference is possible by modifying a function (adding &):
function filter(&$array){ //Note & mark
$array['new_index'] = "Something new" ;
}
$array = array("a"=> "a");
filter($array); //The function now receives the array by reference, not by value.
var_dump($array); //The array should be modified.
Edit:
Make your callback return the filtered array:
$this->EventBus->subscribe('FilterTestEvent', function(&$item){
$item['new'] = 'LoremIpsum';
return $item ;
});
Passing by reference should not work here, because in the source code that $value variable is swapped with another value and returned after.
Ok. I found the answer. The filter function needs to be changed so that it accepts arrays as value, in which I can save the reference. For details see difference Revision 1 and Revision 2 of the Eventbus source code, here: goo.gl/GBocgl
There are numerous questions here asking how to sort a multi-dimensional array in PHP. The answer is usort(). I know that. But I have a question that takes it a bit further, and I couldn't see a similar answer here.
I have an array of records, each of which includes a country ID (or a country name if you prefer; it's not relevant).
My task is to sort the array in such a way as to favour certain countries. This is dynamic -- ie the choice of countries to favour is determined by the user's config. I have a separate array which specifies the required sort order for the first few countries; results from other countries would just be left unsorted at the end of the list.
So the question is: how do I get the this sort criteria into usort() without resorting to using a global variable. And preferably without injecting the criteria array into every element of the main array ('coz if I'm going to loop it anyway, what's the point in using usort() at all?)
Please note: Since it's going to be relevant to the answers here, I'm stuck on PHP 5.2 for the time being, so I can't use an anonymous function. We are in the process of upgrading, but for now I need answers that will work for 5.2. (answers for 5.3/5.4 will be welcome too, especially if they make it significantly easier, but I won't be able to use them)
You explicitly write that you do not want to have global variables, so I do not make you a suggestion with static variables as well because those are actually global variables - and those are not needed at all.
In PHP 5.2 (and earlier) if you need call context within the callback, you can create your context by making use of a class of it's own that carries it:
class CallContext
{
}
For example you have the compare function for sort:
class CallContext
{
...
public function compare($a, $b)
{
return $this->weight($a) - $this->weight($b);
}
public function getCallback()
{
return array($this, 'compare');
}
...
}
That function can be used as the following as a callback with usort then:
$context = new CallContext();
usort($array, $context->getCallback());
Pretty straight forward. The private implementation of CallContext::weight is still missing, and from your question we know it needs some sort data and information. For example the name of the key of the country id in each record. Lets assume records are Stdclass objects so to get the weight of one record the context class needs to know the name of the property, the sort-order you define your own and a sort-value for those country-ids that are not defined in the custom sort order (the others, the rest).
These configuration values are given with the constructor function (ctor in short) and are stored as private members. The missing weight function then converts a record into the sort-value based on that information:
class CallContext
{
private $property, $sortOrder, $sortOther;
public function __construct($property, $sortOrder, $sortOther = 9999)
{
$this->property = $property;
$this->sortOrder = $sortOrder;
$this->sortOther = $sortOther;
}
private function weight($object) {
if (!is_object($object)) {
throw new InvalidArgumentException(sprintf('Not an object: %s.', print_r($object, 1)));
}
if (!isset($object->{$this->property})) {
throw new InvalidArgumentException(sprintf('Property "%s" not found in object: %s.', $this->property, print_r($object, 1)));
}
$value = $object->{$this->property};
return isset($this->sortOrder[$value])
? $this->sortOrder[$value]
: $this->sortOther;
}
...
The usage now extends to the following:
$property = 'country';
$order = array(
# country ID => sort key (lower is first)
46 => 1,
45 => 2
);
$context = new CallContext('country', $order);
usort($array, $context->getCallback());
With the same principle you can very often convert any PHP 5.3 closure with use clauses to PHP 5.2. The variables from the use clause become private members injected with construction.
This variant does not only prevent the usage of static, it also makes visible that you have got some mapping per each element and as both elements are treated equal, it makes use of a private implementation of some weight function which works very well with usort.
I hope this is helpful.
You might not want a global variable, but you need something that behaves like one. You could use a class with static methods and parameters. It won't pollute the global scope that much and it would still function the way you need it.
class CountryCompare {
public static $country_priorities;
public static function compare( $a, $b ) {
// Some custom sorting criteria
// Work with self::country_priorities
}
public static function sort( $countries ) {
return usort( $countries, array( 'CountryCompare', 'compare' ) );
}
}
Then just call it like this:
CountryCompare::country_priorities = loadFromConfig();
CountryCompare::sort( $countries );
You can use closures (PHP >= 5.3):
$weights = array( ... );
usort($records, function($a, $b) use ($weights) {
// use $weights in here as usual and perform your sort logic
});
See Demo : http://codepad.org/vDI2k4n6
$arrayMonths = array(
'jan' => array(1, 8, 5,4),
'feb' => array(10,12,15,11),
'mar' => array(12, 7, 4, 3),
'apr' => array(10,16,7,17),
);
$position = array("Foo1","Foo2","Foo3","FooN");
$set = array();
foreach($arrayMonths as $key => $value)
{
$max = max($value);
$pos = array_search($max, $value);
$set[$key][$position[$pos]] = $max ;
}
function cmp($a, $b)
{
foreach($a as $key => $value )
{
foreach ($b as $bKey => $bValue)
{
return $bValue - $value ;
}
}
}
uasort($set,"cmp");
var_dump($set);
output
array
'apr' =>
array
'FooN' => int 17
'feb' =>
array
'Foo3' => int 15
'mar' =>
array
'Foo1' => int 12
'jan' =>
array
'Foo2' => int 8
another example:-
Sorting a Multi-Dimensional Array with PHP
http://www.firsttube.com/read/sorting-a-multi-dimensional-array-with-php/
Every so often I find myself with a multidimensional array that I want to sort by a value in a sub-array. I have an array that might look like this:
//an array of some songs I like
$songs = array(
'1' => array('artist'=>'The Smashing Pumpkins', 'songname'=>'Soma'),
'2' => array('artist'=>'The Decemberists', 'songname'=>'The Island'),
'3' => array('artist'=>'Fleetwood Mac', 'songname' =>'Second-hand News')
);
The problem is thus: I’d like to echo out the songs I like in the format “Songname (Artist),” and I’d like to do it alphabetically by artist. PHP provides many functions for sorting arrays, but none will work here. ksort() will allow me to sort by key, but the keys in the $songs array are irrelevant. asort() allows me to sort and preserves keys, but it will sort $songs by the value of each element, which is also useless, since the value of each is “array()”. usort() is another possible candidate and can do multi-dimensional sorting, but it involves building a callback function and is often pretty long-winded. Even the examples in the PHP docs references specific keys.
So I developed a quick function to sort by the value of a key in a sub-array. Please note this version does a case-insensitive sort. See subval_sort() below.
function subval_sort($a,$subkey) {
foreach($a as $k=>$v) {
$b[$k] = strtolower($v[$subkey]);
}
asort($b);
foreach($b as $key=>$val) {
$c[] = $a[$key];
}
return $c;
}
To use it on the above, I would simply type:
$songs = subval_sort($songs,'artist');
print_r($songs);
This is what you should expect see:
Array
(
[0] => Array
(
[artist] => Fleetwood Mac
[song] => Second-hand News
)
[1] => Array
(
[artist] => The Decemberists
[song] => The Island
)
[2] => Array
(
[artist] => The Smashing Pumpkins
[song] => Cherub Rock
)
)
The songs, sorted by artist.
The answer to your question is indeed in the usort() function. However, what you need to do is write the function that you pass to it is doing the weighting for you properly.
Most of the time, you have something like
if($a>$b)
{
return $a;
}
But what you need to do is something along the lines of
if($a>$b || $someCountryID != 36)
{
return $a;
}
else
{
return $b;
}
You need to use ksort to sort by weight, not usort. That will be much cleaner.
Arrange your data in an associative array $weighted_data in the format weight => country_data_struct. This is a very intuitive form of presentation for weighted data. Then run
krsort($weighted_data)
I have a list of ids [1,500,7] and a list of entities with corresponding id properties, but in a different order (1 -> 7, 500). In php, how can I sort them according to the list of ids?
Php version is 5.3.2
Given some data structures like the following (from your description):
$ids = array(5, 15, 10);
$values = array(
(object) array('id' => 10, 'data' => 'foo'),
(object) array('id' => 5, 'data' => 'foo'),
(object) array('id' => 15, 'data' => 'foo'),
);
You could use something like the following:
// Precalculate sort positions to avoid two calls to array_search for each sort
// operation as that gets costly very quickly.
$id_positions = array_flip($ids);
// Do the actual sorting here.
usort($values, function($a, $b) use ($id_positions) {
return ($id_positions[$a->id] < $id_positions[$b->id] ? -1 : 1);
});
The above code makes a few assumptions, but should get you on your way.
You can create a compare function (or method inside a class) that should return a positive, negative or 0 value depending if the first value to compare is greater, lesser or equal to the second value. And then call usort() (in this link you'll find more info about the compare function).
Assuming that the list of IDs and the list of entities are the same length and that every ID has a corresponding entity and that every entity's ID is in the ID list.
$sorted_entities = array();
$sort_order = array_combine($list_of_ids, range(0, count($list_of_ids) - 1));
foreach ($list_of_entities as $entity) {
$sorted_entities[$sort_order[$entity->id]] = $entity;
}
This has the advantage of traversing each array only once. It has the disadvantage that it does not sort the entities in place.