As seen in this other answer, there are several ways to iterate two same-sized arrays simultaneously; however, all of the methods have a rather significant pitfall. Here are some of the caveats with the methods suggested:
You can't use FALSE values in one of the arrays.
You can only use scalar values in one of the arrays.
You must use numerically indexed arrays.
Both arrays must share the same keys.
Etc.
My question is - is there a method for doing this which doesn't suffer from any of these (or other) significant caveats?
Bear in mind that I'm simply asking this out of curiosity; I have no use-case in mind, nor do I even know if such a case actually exists or would be useful/practical in a real-world scenario. However, here is some example data:
$arr1 = [ 'a' => 1, 'b' => FALSE, 'c' => new DateTime() ];
$arr2 = [ 'foo', TRUE, 7 ];
You can use a MultipleIterator:
$iterator = new MultipleIterator;
$iterator->attachIterator(new ArrayIterator($array1));
$iterator->attachIterator(new ArrayIterator($array2));
foreach ($iterator as $values) {
var_dump($values[0], $values[1]);
}
You can find more examples concerning the various options in the docs.
As of PHP 5.5 you can do this:
foreach (array_map(null, $array1, $array2) as list($item1, $item2))
{
var_dump($item1);
var_dump($item2);
}
http://us3.php.net/manual/en/control-structures.foreach.php#control-structures.foreach.list
<?php
$arr1 = array( 'a' => 1, 'b' => FALSE, 'c' => new DateTime() );
$arr2 = array( 'foo', TRUE, 7, 5 );
reset($arr1);
reset($arr2);
while ( (list($key, $val) = each($arr1))
&& (list($key2, $val2) = each($arr2))
) {
var_dump($val,$val2);
// or whatever you wanted to do with them
}
http://www.php.net/manual/en/function.each.php
Related
I have two arrays, for example $session and $post with 100+ values. I will compare the $post array values with $session array. If post is different then it will be taken to result array else not.
We can try this using array_diff_assoc($post, $session) and foreach(). Which one is faster?
For profiling, Phil has suggested a great way in his reply, but I will link it here too, just in case:
Simplest way to profile a PHP script
Practically, you need to know what each approach does. in array_diff_assoc, you are returning the difference between 2 collections, after comparing the key/value couples for each element. It will then return an array that contains the entries from array1 that are not present in array2 or array3, etc.
In a for each loop, you will need to hard code the same function (assuming that's what you need). You will need to take the first element, then look for the combination in your other arrays. If it matches your requirements, you will save it into your output array, or even print it directly.
Same principles apply, but then again, it will be up to profiling to determine the faster approach. Try doing so on a large number of big arrays, as the difference isn't noticeable at smaller scales.
I'll leave this as a stub/example, please edit, or use for profiling.
<?php
$before = [
'name' => 'Bertie',
'age' => '23'
];
$after = [
'name' => 'Harold',
'age' => '23',
'occupation' => 'Bus driver'
];
function changed_1($after, $before) {
return array_diff_assoc($after, $before);
}
function changed_2($after, $before) {
$changed = [];
foreach($after as $k => $v) {
if(isset($before[$k]) && $before[$k] !== $v)
$changed[$k] = $v;
if(!isset($before[$k]))
$changed[$k] = $v;
}
return $changed;
}
var_export(changed_1($after, $before));
var_export(changed_2($after, $before));
Output:
array (
'name' => 'Harold',
'occupation' => 'Bus driver',
)array (
'name' => 'Harold',
'occupation' => 'Bus driver',
)
Using the numbers from $ids, I want to pull the data from $nuts.
So for example:
$ids = [0,3,5]; // 0 calories, 3 sugar, 5 fat
$nuts = [
'calories' => 'cal',
'protein' => 'pro',
'carbohydrate' => 'car',
'sugar' => 'sug',
'fiber' => 'fib',
'fat' => 'fat',
];
$returnData = [
'calories' => 'cal',
'sugar' => 'sug',
'fat' => 'fat',
];
I could loop through each $ids number with a foreach(); but I'm curious to see if there is a better method than this?
$newNuts = array_values(array_flip($nuts));
foreach($ids as $i)
$returnData[$newNuts[$i]] = $nuts[$newNuts[$i]];
I did some work and realized, you don't need array_flip, array_values is fine.
$num_nuts = array_values ($nuts);
for ($z=0; $z<sizeof($ids); $z++) {
echo $num_nuts[$ids[$z]];
}
Just 1 more line of code, but I think it does the job. I think mine is going to be faster because the array_flip basically exchanges all keys with their associated values in an array, which is not what I am doing. It's actually one less pain.
I am simply converting the original array to a new one by index and simply looping upon it. Also, not the elegant way to use the power of PHP available to us, but works just fine. array_flip is O(n), but I think better not use it for larger data-sets.
How about a simple array_slice?
$result = array();
foreach ($ids as $i) {
$result += array_slice($nuts, $i, 1, true);
}
No need to create a copy of the array.
I have two arrays as shown below. I need to merge the content of the arrays so that I can get the structure as shown in the third array at last. I have checked array_merge but can't figure out the way this is possible. Any help appreciated. Thanks.
[
['gross_value' => '100', 'quantity' => '1'],
['gross_value' => '200', 'quantity' => '1']
]
and
[
['item_title_id' => '1', 'order_id' => '4'],
['item_title_id' => '2', 'order_id' => '4']
];
I should get a merged array like this:
[
[
'gross_value' => '100',
'quantity' => '1',
'item_title_id' => '1',
'order_id' => 4
],
[
'gross_value' => '200',
'quantity' => '1',
'item_title_id' => '2',
'order_id' => 4
]
]
Use array_merge_recursive :
Convert all numeric key to strings, (make is associative array)
$result = array_merge_recursive($ar1, $ar2);
print_r($result);
See live demo here
how about:
$arr1 = array(
0 => array(
'gross_value' => '100',
'quantity' => '1'
),
1 => array(
'gross_value' => '200',
'quantity' => '1'
)
);
$arr2 = array(
0 => array(
'item_title_id' => '1',
'order_id' => '4'
),
1 => array(
'item_title_id' => '2',
'order_id' => '4'
)
);
$arr = array();
foreach($arr1 as $k => $v) {
array_push($arr, array_merge($v, $arr2[$k]));
}
print_r($arr);
output:
Array
(
[0] => Array
(
[gross_value] => 100
[quantity] => 1
[item_title_id] => 1
[order_id] => 4
)
[1] => Array
(
[gross_value] => 200
[quantity] => 1
[item_title_id] => 2
[order_id] => 4
)
)
Have a look at array_merge
I would probably iterate over the arrays and merge them manually.
$result = array();
foreach ( $array1 as $key => $item )
{
$result[$key] = array_merge($array1[$key], $array2[$key]);
}
You will have an issue if the top-level arrays don't have strictly matching keys though.
If you have $array1 and $array2, try this:
foreach($array1 as $key1=>$innerArray){
$array1[$key1]['item_title_id'] = $array2[$key1]['item_title_id'];
$array1[$key1]['order_id'] = $array2[$key1]['order_id'];
}
The problem with things like merge recursive is that they don't know when to stop.
In some scenarios you want to stop traversing down an array and simply take a given value if it exists.
For instance if you have to override a nested config array you might not want the default keys to stick around at a a specific level.
here is my solution:
public static function merge_lvl2(){
$args = func_get_args();
return static::merge($args, 2);
}
public static function merge($args, $maxDepth = null, $depth = 1)
{
$merge = [];
foreach($args as $arg) {
if (is_array($arg)) {
if (is_array($merge)) {
if ($maxDepth == $depth) {
$arg += $merge;
$merge = $arg;
} else {
$merge = array_merge($merge, $arg);
}
} else {
$merge = $arg;
}
}
}
if ($maxDepth !== $depth) {
foreach($args as $a) {
if (is_array($a)) {
foreach($a as $k => $v) {
if (isset($merge[$k]) && is_array($merge[$k])) {
$merge[$k] = static::merge([$merge[$k], $v], $maxDepth, $depth + 1);
}
}
}
}
}
return $merge;
}
You can pass as many arrays to merge as you want to.
$merged = ClassName::merge_lvl2([..array1..], [..array2..], [..array3..], etc...);
It will stop merging at level 2 and accept the last instance of the key as an override instead of a merge.
You can also call merge directly with an array of args and setting the max depth.
If no max depth is set it will traverse the entire array.
The most modern, elegant, concise way to merge rows from two or more arrays (or the rows from a multidimensional array with 3 or more levels of depth) is to call array_merge() on each row (array_replace() can also be used). array_map() can call array_merge by its string name and the input data can be split into individual arguments with the "spread operator" (...) when needed.
Code for the OP's arrays: (Demo)
var_export(
array_map('array_merge', $arr1, $arr2)
);
The above technique will return a newly indexed array (though you might not notice because the sample input arrays were indexed to begin with). If your input data has associative first-level keys, they will be ignored and destroyed by this technique. If you have non-numeric first-level keys and want to merge on those, then array_merge_recursive() is likely to be the ideal native function - Demo.
However, it must be said, that for the OP's sample data array_merge_recursive() IS NOT a correct technique.
My first snippet is conveniently extended if you have more than two arrays which need their rows to be merge based on their positions. (Demo)
var_export(
array_map('array_merge', $arr1, $arr2, $arr3)
);
And as mentioned earlier, the spread operator can be used to unpack deeper arrays with the same result. Again, the number of subarrays containing rows can be dynamic. If your deep array only has one subarray containing rows, then the result will be a "flattening" effect where the top level is removed.
Code with new data structure: (Demo)
$masterArray = [
[
['gross_value' => '100', 'quantity' => '5'],
['gross_value' => '200', 'quantity' => '6']
],
[
['item_title_id' => '1', 'order_id' => '3'],
['item_title_id' => '2', 'order_id' => '4']
],
[
['foo' => 'bar1'],
['foo' => 'bar2']
]
];
var_export(
array_map('array_merge', ...$masterArray)
);
To be fair, array_replace_recursive() does provide the desired result using the OP's sample data, but I find the technique to be semantically misleading. (Demo)
All that said, you are not forced to use PHP's native array functions; you can use classic loops as well -- you will have several ways to "unite" the rows inside the loop. This approach is a little less D.R.Y. because you need to explicitly specific the separate arrays that you wish to synchronously iterate. Just make sure that you understand the nuanced differences in using array_merge(), array_replace(), and the union operator (+) with different qualities of data. Hint: associative, non-numeric keyed data in the respective rows will be affected when key collisions occur. Be careful to use a merging technique that will not overwrite the wrong data when rows share associative keys.
array_merge() to build a new array: (array_merge() Demo) (array_replace() Demo) (array union operator + Demo)
$result = [];
foreach ($arr1 as $i => $row) {
$result[] = array_merge($row, $arr2[$i]);
}
var_export($result);
Alternative, you can use the same general approach, but instead of populating a new $result array, you can merge data into the first array.
(array_merge() Demo) (array_replace() Demo) (array union assignment operator += Demo)
foreach ($arr1 as $i => &$row) {
$row = array_merge($row, $arr2[$i]);
}
var_export($arr1);
For the sake of completeness, if you have an indexed array of indexed arrays, then you might even use iterated calls of array_push() with the spread operator to achieve a similar functionality. This quite literally, indicatively appends the row data from subsequent arrays to the first array's rows.
Code: (Demo)
$arr1 = [
['A', 'B', 'C'],
['F', 'G']
];
$arr2 = [
['D', 'E'],
['H', 'I', 'J', 'L']
];
foreach ($arr1 as $i => &$row) {
array_push($row, ...$arr2[$i]);
}
var_export($arr1);
Related non-duplicate content on Stack Overflow:
Partially merge one array's row data with another another array:Add column of values from one array to another
Merge two flat arrays to create an array of merged rows:Transforming array values in elements of a subarray using PHP
Merge rows with indexed elements, remove duplicates and reindex:Merge two multidimensional arrays, preserve numeric keys, and combine values inside array
Merge arrays containing objects:Merge rows of two arrays containing objects by first level index
Push single elements from one array to rows in another array:Push elements from one array into rows of another array (one element per row)
On the above pages, the rabbit hole goes further because I've linked other related pages to them. Keep researching until you find what you need.
If you are using Laravel, you might be interested in its combine() and collect() methods.
I have two arrays,
The $first has 5000 arrays inside it and looks like:
array(
array('number' => 1),
array('number' => 2),
array('number' => 3),
array('number' => 4),
...
array('number' => 5000)
);
and the $second has 16000 rows and looks like:
array(
array('key' => 1, 'val' => 'something'),
array('key' => 2, 'val' => 'something'),
array('key' => 3, 'val' => 'something'),
...
array('key' => 16000, 'val' => 'something'),
)
I want to create a third array that contains $second[$i]['val'] IF $second[$i][$key] is in $first[$i][$number]
currently I am doing:
$third = array();
foreach($first as &$f)
$f = $f['number'];
foreach($second as $s){
if(in_array($s['key'], $first)
$third[] = $s['val];
}
but, unless I use php's set_timeout(0) it is timing out, is there a more efficient way?
$third = array();
$ftemp = array();
foreach($first as $f)
$ftemp[$f['number']] = true;
foreach($second as $s){
if(isset($ftemp[$s['key']]))
$third[] = $s['val'];
}
should be waaay faster.
Don't try to make lookup dictionary in more convoluted way like below, because it actually is slower than above straightforward loop:
$third = array();
$ftemp = array_flip(reset(call_user_func_array('array_map', array_merge(array(null), $first))));
// $ftemp = array_flip(array_map('reset', $first)); // this is also slower
// array_unshift($first, null); $ftemp = array_flip(reset(call_user_func_array('array_map', $first))); // and this is even slower and modifies $first array
foreach($second as $s){
if(isset($ftemp[$s['key']]))
$third[] = $s['val'];
}
It's probably serious nitpicking but you could replace the foreach with a for which is a little faster, but i doubt that will make a big difference. You are working on a big dataset which might simply be not really fast to process on a webserver.
You are asking for "intersections" between the two arrays but on specific column keys which are not identical. Not to worry, PHP has a native function that is optimized under the hood for this task. array_uintersect() with no special data preparation. Within the custom callback function, null coalesce to the opposite array's key name. The reason for this fallback is because $a and $b do not represent array1 and array2. Because the intersect/diff family of native array functions sort while they filter, there may be instances where column values from the same array will be compared against each other. Again, this is part of the source code optimization.
Code: (Demo)
var_export(
array_uintersect(
$keyValues,
$numbers,
fn($a, $b) => ($a['number'] ?? $a['key']) <=> ($b['number'] ?? $b['key'])
)
);
As a general rule, though, if you are going to make a lot of array comparisons and speed matters, it is better to make key-based comparisons instead of value-based comparisons. Because of the way that PHP handles arrays as hashmaps, key-comparison functions/processes always outpace their value-comparing equivalent.
If you need to isolate the val column data after filtering, array_column() will fix this up for you quickly.
I am trying to compare to multidimensional arrays, but I can't just use array_diff_assoc(). The arrays I am trying to compare are both associative arrays, and they are both sorted so the keys are in the same order. For the most part the arrays are identical in structure. I can't seem to figure out how to compare the elements that store arrays, I can compare the elements that hold one value just fine does anyone know what I can do?
If your trying to just see if they are different (and not what specifically is different) you could try something like:
return serialize($array1) == seralize($array2);
That would give you a yea or neah on the equality of the two arrays.
It's not clear whether you want to see if they're equal, or actually want an output of what the differences are.
If it's the former then you could do it the proper way, with a recursive function:
$array1 = array('a' => 1, 'b' => 2, 'c' => array('ca' => 1, 'cb' => array('foo')));
$array2 = array('a' => 1, 'b' => 2, 'c' => array('ca' => 1, 'cb' => array('bar')));
var_dump(arrayEqual($array1, $array2));
function arrayEqual($a1, $a2)
{
if (count(array_diff($a1, $a2)))
return false;
foreach ($a1 as $k => $v)
{
if (is_array($v) && !arrayEqual($a1[$k], $a2[$k]))
return false;
}
return true;
}
Or use a complete hack like this:
if (serialize($array1) == serialize($array2))