I have an array that carries a definite number of dimensions so I'm not really looking at something recursive (Unless maybe for maintainability sake in the future). It's a numeric array gotten from the database with each row holding another array. Each of those level 2 arrays contain strings like
var1, var2 , var3
And so on. Note the irregular appearance of commas in the string. So I intend to break the comma delimited string in the third level then log them in the final array but I get an error saying I am supplying an null array. So I want to know why it says the array is null and how I can make it recognise that as a valid array. My code goes below:
function fetch_each($arr) {
$temp = array();
for ($i = 0; $i < count($arr); $i++) {
for ($j = 0; $j < count($arr[$i]); $j++) {
array_reduce(preg_split("/[\s,]+/", $arr[$i][$j]), function($a, $b) {
return array_push($temp, $a, $b);
});
}
}
return $temp;
}
PS: Please don't mark as duplicate. I don't want to copy someone else's code but want to understand why this does not work. Thanks.
You have this problem because $temp is not visible in the function block.
To solve that, you must use the keyword use (variable_name) next to the function definition as in this example :
array_reduce(preg_split("/[\s,]+/", $arr[$i][$j]), function($a, $b) use (&$temp) {
return array_push($temp, $a, $b);
});
Just a remark, $a will contain the result of array_push
Returns:int the new number of elements in the array.
So you can remove it from the array_push() instruction to keep a clean array with only splitted strings
Related
Edit1: The problem: I want to convert in php a associative array to a indexed one. So I can return it via json_encode as an array and not as an object. For this I try to fill the missing keys. Here the description:
Got a small problem, I need to transfer a json_encoded array as an array to js. At the moment it returns an Object. I´m working with Angular so I really need an Array. I try to explain it as much as possible.
$arrNew[0][5][0][0][1]["id"] = 1;
//$arrNew[0][0][0][0][1] = "";
//$arrNew[0][1][0][0][1] = "";
//$arrNew[0][2][0][0][1] = "";
//$arrNew[0][3][0][0][1] = "";
//$arrNew[0][4][0][0][1] = "";
$arrNew[0][5][0][0][1]["name"] = 'Test';
var_dump($arrNew);
So if I return it now It returns the second element as object cause of the missing index 0-4 and the 4th element cause of the missing index 0 (associative array -> object)
So if I uncomment the block it works like a charm. Now I have the problem its not every time the element 5 sometime 3, 4 or something else so I build a function which adds them automaticly:
$objSorted = cleanArray($arrNew);
function cleanArray($array){
end($array);
$max = key($array) + 1; //Get the final key as max!
for($i = 0; $i < $max; $i++) {
if(!isset($array[$i])) {
$array[$i] = '';
} else {
end($array[$i]);
$max2 = key($array[$i]) + 1;
for($i2 = 0; $i2 < $max2; $i2++) {
.... same code repeats here for every index
So if I vardump it it returns:
The problem:
On js side its still an object, what I also see is that the elements are not sorted. So I think somehow PHP sees it still as an associative array. Any clue why this happens ? The key is set with the index of the loop and has to be a integer value.
PS: I know reworking it in JS is possible but would have be done nearly on every request with a huge load of loops
If I understand your problem, you create a sparse multidimensional array of objects. Because the arrays have gaps in the keys, json_encode() produces objects on some levels but you need it to produce arrays for all but the most inner level.
The following function fills the missing keys (starting from 0 until the maximum value used as numeric key in an array) on all array levels. It then sorts each array by their keys to make sure json_encode() encodes it as array and not object.
The sorting is needed, otherwise json_encode() generates an object; this behaviour is explained in a note on the json_encode() documentation page:
When encoding an array, if the keys are not a continuous numeric sequence starting from 0, all keys are encoded as strings, and specified explicitly for each key-value pair.
// If $arr has numeric keys (not all keys are tested!) then returns
// an array whose keys are a continuous numeric sequence starting from 0.
// Operate recursively for array values of $arr
function fillKeys(array $arr)
{
// Fill the numeric keys of all values that are arrays
foreach ($arr as $key => $value) {
if (is_array($value)) {
$arr[$key] = fillKeys($value);
}
}
$max = max(array_keys($arr));
// Sloppy detection of numeric keys; it may fail you for mixed type keys!
if (is_int($max)) {
// Fill the missing keys; use NULL as value
$arr = $arr + array_fill(0, $max, NULL);
// Sort by keys to have a continuous sequence
ksort($arr);
}
return $arr;
}
// Some array to test
$arrNew[0][5][0][0][1]["id"] = 1;
$arrNew[0][3][0][2][1]["id"] = 2;
$arrNew[0][5][0][0][1]["name"] = 'Test';
echo("============= Before ==============\n");
echo(json_encode($arrNew)."\n");
$normal = fillKeys($arrNew);
echo("============= After ==============\n");
echo(json_encode($normal)."\n");
The output:
============= Before ==============
[{"5":[[{"1":{"id":1,"name":"Test"}}]],"3":[{"2":{"1":{"id":2}}}]}]
============= After ==============
[[null,null,null,[[null,null,[null,{"id":2}]]],null,[[[null,{"id":1,"name":"Test"}]]]]]
The line $arr = $arr + array_fill(0, $max, NULL); uses NULL as values for the missing keys. This is, I think, the best for the Javascript code that parses the array (you can use if (! arr[0]) to detect the dummy values).
You can use the empty string ('') instead of NULL to get a shorter JSON:
[["","","",[["","",["",{"id":2}]]],"",[[["",{"id":1,"name":"Test"}]]]]]
but it requires slightly longer code on the JS side to detect the dummy values (if (arr[0] != '')).
I have an Array with 8 arrays inside.
It looks like this:
[[num,...],[num,...],[num,...],[num,...],[num,...],[num,...],[num,...],[num,...]]
Each of this inner arrays has as its first element a number. Now I want to receive the element of the outer array with the biggest number as first element.
How do I do that?
Thank you very much.
You can define any sorting algorithm by using PHP's usort()
usort($array, function($a, $b) {
return $a[0] > $b[0];
});
This will sort your array, in place, such that the first element will have the largest number as it's first element.
It's not necessary (and is much more expensive) to sort the entire array. Something like this would work:
// initially, regard the first element as the largest
$element = $array[0];
$greatest = $array[0][0];
$length = count($array);
// compare the first value of each array against $greatest, swapping $element if it's larger
for($i = 1; $i < $length; $i++) { // N.B. start with second element
if($array[$i][0] > $greatest) {
$element = $array[$i];
}
}
// $element is now the element with the biggest first value
Check out usort : http://php.net/manual/en/function.usort.php
You'll have to write your own comparison function.
I have 4 arrays and use array_multisort to sort them all at the same time relative to one another.
Problem is, in the first array, there can be empty values and I want to put them at the end, not the beginning.
Example : http://codepad.org/V6TjCsS5
Is there a way to:
Pass a custom function to array_multisort
or
Sort the first array with a custom function then use the result order to sort the other arrays
or
Use a certain argument with array_multisort to achieve what I want
Thank you very much
Unfortunately none of the approaches your propose is possible, which means you have to take another step back and look for alternatives. I am assuming you want a normal ascending sort, with the explicit exception that empty elements (which you be "smallest") need to be considered as "largest".
Option 1: Manually rearrange elements after sorting
Do your array_multisort as usual, and then make the modifications you require:
// $arr1, $arr2 etc have been sorted with array_multisort
while(reset($arr1) == '') {
$k = key($arr1);
unset($arr1[$k]); // remove empty element from beginning of array
$arr1[$k] = ''; // add it to end of array
// and now do the same for $arr2
$v = reset($arr2);
$k = key($arr2);
unset($arr2[$k]);
$arr2[$k] = $v;
// the same for $arr3, etc
}
You can pull out part of the code in a function to make this prettier:
function shift_and_push(&$arr) {
$v = reset($arr);
$k = key($arr);
unset($arr[$k]);
$arr[$k] = $v;
}
Option 2: Condense everything inside one array so you can use usort
The idea here is to pull all your arrays into one so you can specify the comparison function by using usort:
$allArrays = array_map(function() { return func_get_args(); },
$array1, $array2 /* , as many arrays as you want */);
You can now sort:
// writing this as a free function so that it looks presentable
function cmp($row1, $row2) {
// $row1[0] is the item in your first array, etc
if($row1[0] == $row2[0]) {
return 0;
}
else if($row1[0] == '') {
return 1;
}
else if($row2[0] == '') {
return -1;
}
return $row1[0] < $row2[0] ? -1 : 1;
}
usort($allArrays, "cmp");
At this point you are left with an array, each element (row) of which is an array. The first elements of each are what was originally inside $array1, second elements are what was in $array2, etc. By placing those elements inside "rows", we have managed to keep the sort order among all your original arrays synchronized.
The second argument to array_multisort can be the options to the sort. So you could pass SORT_DESC if SORT_ASC is doing the opposite of what you want.
array_multisort($arr, SORT_DESC);
For completeness sake, here are the other options SORT_ASC, SORT_DESC, SORT_REGULAR, SORT_NUMERIC, SORT_STRING. SORT_STRING may be helpful.
Do you actually want the empty elements? Just remove them before sorting:
foreach($array1 as &$v) {
if($v==='')
{
unset($v);
}
}
A non-empty zero-indexed array A consisting of N integers is given. The first covering prefix of array A is the smallest integer P such that $0 \leq P < N$ and such that every value that occurs in array A also occurs in sequence $A[0], A[1], \ldots, A[P]$.
For example, the first covering prefix of array A such that
A[0]=2 A[1]=2 A[2]=1 A[3]=0 A[4]=1
is 3, because sequence A[0], A[1], A[2], A[3] equal to 2, 2, 1, 0 contains all values that occur in array A.
Write a function
int ps(int[] A);
that given a zero-indexed non-empty array A consisting of N integers returns the first covering prefix of A. Assume that $N <= 1,000,000$. Assume that each element in the array is an integer in range [0..N-1].
For example, given array A such that A[0]=2 A[1]=2 A[2]=1 A[3]=0 A[4]=1
the function should return 3, as explained in the example above.
This is a very short solution. Pretty but won't scale well.
function ps($A) {
$cp = 0; // covering prefix
$unique = array_unique($A); // will preserve indexes
end($unique); // go to end of the array
$cp = key($unique); // get the key
return $cp;
}
Here's a simple way :
function covering_prefix ( $A ) {
$in=array();
$li=0;
$c=count($A);
for($i=0 ;$i<$c ; $i++){
if (!isset($in[$A[$i]])){
$in[$A[$i]]='1';
$li=$i;
}
}
return $li;
}
Here is a solution using ruby
def first_covering_prefix(a)
all_values = a.uniq
i = 0
a.each do |e|
all_values.delete(e)
if all_values.empty?
return i
end
i = i + 1
end
end
it's a 83% answer, because of use of in_array, a better solution already proposed by ronan
function solution($A) {
// write your code in PHP5
$in=array();
$li=0;
for ($i=0; $i < count($A); $i++) {
# code...
if (!in_array($A[$i], $in)){
$in[]=$A[$i];
$li=$i;
}
}
return $li;
}
This code does not run properly, but it suggests what I am trying to do:
function sort_2d_by_index($a,$i) {
function cmp($x, $y) {
// Nested function, can't find $i
// (global $i defeats the purpose of passing an arg)
if ($x[$i] == $y[$i]) { return 0; }
return ($x[$i] < $y[$i]) ? -1 : 1;
}
usort($a,"cmp");
return $a;
}
There HAS to be a much better way to do this. I've been examining ksort(), multisort(), and all sorts of sorts until I'm sort of tired trying to sort it all out.
The situation is this: I've got a 2-d array...
array(
array(3,5,7),
array(2,6,8),
array(1,4,9)
);
...and I want to sort by a column index. Say, column [1], would give this result:
array(
array(1,4,9),
array(3,5,7),
array(2,6,8)
);
Does someone have a link (I'm sure this has been asked before), or could someone say "you need foosort, definitely". Thanks very much.
In the documentation of array_multisort it is mentioned that it can be used for this kind of thing.
You can't avoid creating an array that consists of only one column:
$sort_column = array();
foreach ($a as $row)
$sort_column []= $row[1]; // 1 = your example
array_multisort($sort_column, $a);
This sorts both arrays synchronously so that afterwards your whole array is sorted in the same order as the $sort_column array is.
As of PHP 5.3 you can use a closure (pass $i into the function) by defining your cmp function like this:
$cmp = function($x, $y) use ($i) { ... };
You can use use to access $i:
function cmp($x, $y) use ($i) {
// $i now available
if ($x[$i] == $y[$i]) { return 0; }
return ($x[$i] < $y[$i]) ? -1 : 1;
}
http://www.php.net/manual/en/function.sort.php#99419
phpdotnet at m4tt dot co dot uk
Simple function to sort an array by a specific key. Maintains index association.