I am trying to explode an array and then shuffle 4 items at a time so that each array appears in random order.
It half works but on refresh sometimes it shows only 2 or 3 arrays not 4. Is there an easy workaround for it?
Thanks in advance.
$siteswith = $row['siteswith'];
$array = explode(',', $siteswith);
shuffle($array);
foreach(array_slice($array, 0, 4) as $item ){
}
It seems that $array does not have enough items that the slice function can "slice" from. Please check if your input string $row['siteswith'] always provide 4 or more comma separated values.
Depending what the code is later used for, you could also use array_rand() to pick n random elements from the list
$siteswith = $row['siteswith'];
$array = explode(',', $siteswith);
foreach(array_rand($array, 4) as $item ){
...
}
This will also prevent mutating your origin array (other than array_shift will do) which avoids unexpected behaviour.
Please be aware that you'll receive an exception when the array size is smaller than the requested amount of random elements.
Related
The following is the code
<?php
$id ="202883-202882-202884-0";
$str = implode('-',array_unique(explode('-', $id)));
echo $str;
?>
The result is
202883-202882-202884-0
for $id ="202883-202882-202882-0";, result is 202883-202882-0
I would like to replace the duplicate value with zero, so that the result should be like 202883-202882-0-0, not just remove it.
and for $id ="202883-0-0-0";, result should be 202883-0-0-0. zero should not be replaced, repeating zeros are allowed.
How can I archive that?
More info:
I want to replace every duplicate numbers. Because this is for a product comparison website. There will be only maximum 4 numbers. each will be either a 6 digit number or single digit zero. all zero means no product was selected. one 6 digit number and 3 zero means, one product selected and 3 blank.
Each 6 digit number will collect data from database, I dont want to allow users to enter same number multiple times (will happen only if the number is add with the URL manually.).
Update: I understand that my question was not clear, may be my English is poor.
Here is more explanation, this function is for a smartphone comparison website.
The URL format is sitename.com/compare.html?id=202883-202882-202889-202888.
All three numbers are different smartphones(their database product ID).
I dont want to let users to type in the same product ID like id=202883-202882-202882-202888. It will not display two 202882 results in the website, but it will cause some small issues. The URL will be same without change, but the internal PHP code should consider it as id=202883-202882-202888-0.
The duplicates should be replaced as zero and added to the end.
There will be only 4 numbers separated by "-".
The following examples might clear the cloud!
if pid=202883-202882-202889-202888 the result should be 202883-202882-202889-202888
if pid=202883-202883-202883-202888 the result should be 202888-0-0-0
if pid=202883-202882-202883-202888 the result should be 202883-202882-202888-0
if pid=202882-202882-202882-202882 the result should be 202882-0-0-0
I want to allow only either 6 digit numbers or single digit zero through the string.
if pid=rgfsdg-fgsdfr4354-202883-0 the result should be 202883-0-0-0
if pid=fasdfasd-asdfads-adsfds-dasfad the result should be 0-0-0-0
if pid=4354-45882-445202882-202882 the result should be 202882-0-0-0
It is too complicated for me create, I know there are bright minds out there who can do it much more efficiently than I can.
You can do a array_unique (preserves key), then fill the gaps with 0. Sort by key and you are done :)
+ on arrays will unify the arrays but prioritizes the one on the left.
Code
$input = "0-1-1-3-1-1-3-5-0";
$array = explode('-', $input);
$result = array_unique($array) + array_fill(0, count($array), 0);
ksort($result);
var_dump(implode('-',$result));
Code (v2 - suggested by mickmackusa) - shorter and easier to understand
Fill an array of the size of the input array. And replace by leftover values from array_unique. No ksort needed. 0s will be replaced at the preserved keys of array_unique.
$input = "0-1-1-3-1-1-3-5-0";
$array = explode('-', $input);
$result = array_replace(array_fill(0, count($array), 0), array_unique($array));
var_export($result);
Working example.
Output
string(17) "0-1-0-3-0-0-0-5-0"
Working example.
references
ksort - sort by key
array_fill - generate an array filled with 0 of a certain length
This is another way to do it.
$id = "202883-202882-202882-0-234567-2-2-45435";
From the String you explode the string into an array based on the delimiter which in this case is '-'/
$id_array = explode('-', $id);
Then we can loop through the array and for every unique entry we find, we can store it in another array. Thus we are building an array as we search through the array.
$id_array_temp = [];
// Loop through the array
foreach ($id_array as $value) {
if ( in_array($value, $id_array_temp)) {
// If the entry exists, replace it with a 0
$id_array_temp[] = 0;
} else {
// If the entry does not exist, save the value so we can inspect it on the next loop.
$id_array_temp[] = $value;
}
}
At the end of this operation we will have an array of unique values with any duplicates replaced with a 0.
To recreate the string, we can use implode...
$str = implode('-', $id_array_temp);
echo $str;
Refactoring this, using a ternary to replace the If,else...
$id_array = explode('-', $id);
$id_array_temp = [];
foreach ($id_array as $value) {
$id_array_temp[] = in_array($value, $id_array_temp) ? 0 : $value;
}
$str = implode('-', $id_array_temp);
echo $str;
Output is
202883-202882-0-0-234567-2-0-45435
This appears to be a classic XY Problem.
The essential actions only need to be:
Separate the substrings in the hyphen delimited string.
Validate that the characters in each substring are in the correct format AND are unique to the set.
Only take meaningful action on qualifying value.
You see, there is no benefit to replacing/sanitizing anything when you only really need to validate the input data. Adding zeros to your input just creates more work later.
In short, you should use a direct approach similar to this flow:
if (!empty($_GET['id'])) {
$ids = array_unique(explode('-', $_GET['id']));
foreach ($ids as $id) {
if (ctype_digit($id) && strlen($id) === 6) {
// or: if (preg_match('~^\d{6}$~', $id)) {
takeYourNecessaryAction($id);
}
}
}
Looking the function below:
function CustomShuffle($arr, $para){
............................
............................
return $array;
}
Suppose this is an array:
$array = array("red","green","blue","yellow","purple");
looking output something like below (May be different ordered but must be same for same integer parameter)
$result = CustomShuffle($array, 10);
// output: array("blue","purple","yellow","red","green") same
$result = CustomShuffle($array, 12);
// output: array("purple","yellow","red","green","blue")
$result = CustomShuffle($array, 10);
// output: array("blue","purple","yellow","red","green") same
$result = CustomShuffle($array, 7);
// output: array("blue","yellow","purple","red","green")
Simply, array will be shuffled with respect to integer parameter but output will be same for same parameter. Is it possible?
Yes this is possible, how it happens does come down to a desired implementation and how many permutations you wish to allow. A very naive method of accomplishing this is to have a loop that runs $para times within CustomShuffle that would array_shift() an element then array_push() that same element. This method would only give you count($array) possible outcomes, meaning numbers congruent modulo count($array) would produce the same result.
The optimal algorithm would allow you to take advantage of the maximum combinations, which would be gmp_fact(count($array)), or simply the factorial of the length of the input array. There is no possible way to achieve more unique combinations than this value, so no matter what algorithm you design, you will always have a constraint on the value of $para until you eventually encounter a combination already seen.
Let's say I have an array like so:
array(
[0]=>1
[1]=>3
[3]=>5
[15]=>6
);
Arbitrarily I want array[15] to be the first:
array(
[15]=>6
[0]=>1
[1]=>3
[3]=>5
);
What is the fastest and most painless way to do this?
Here are the things I've tried:
array_unshift - Unfortunately, my keys are numeric and I need to keep the order (sort of like uasort) this messes up the keys.
uasort - seems too much overhead - the reason I want to make my element the first in my array is to specifically avoid uasort! (Swapping elements on the fly instead of sorting when I need them)
Assuming you know the key of the element you want to shift, and that element could be in any position in the array (not necessarily the last element):
$shift_key = 15;
$shift = array($shift_key => $arr[$shift_key]);
$arr = $shift + $arr;
See demo
Updated - unset() not necessary. Pointed out by #FuzzyTree
You can try this using a slice and a union operator:
// get last element (preserving keys)
$last = array_slice($array, -1, 1, true);
// put it back with union operator
$array = $last + $array;
Update: as mentioned below, this answer takes the last key and puts it at the front. If you want to arbitrarily move any element to the front:
$array = array($your_desired_key => $array[$your_desired_key]) + $array;
Union operators take from the right and add to the left (so the original value gets overwritten).
If #15 is always last you can do
$last = array_pop($array); //remove from end
array_unshift($last); //push on front
To reorder the keys for sorting simply add
$array = array_values($array); //reindex array
#Edit - if we don't assume its always last then I would go with ( if we always know wwhat the key is, then most likely we will know its position or it's not a numerically indexed array but an associative one with numeric keys, as op did state "arbitrarily" so one has to assume the structure of the array is known before hand. )
I also dont see the need to reindex them as the op stated that it was to avoid sorting. So why would you then sort?
$item = $array[15];
unset($array[15]); //....etc.
occurrence of A----5 times
occurrence of B----7 times
occurrence of C----6 times
($total['A']=5;
$total['B']=7;
$total['C']=6;)
I need to rate each based on their occurrence as follows,
$rating['A']=3;
$rating['B']=1;//most occurrence will get rate 1.
$rating['C']=2;
asort(&$total);
$rating = 1;
foreach (array_reverse($total) as $key => $val)
$total[$key] = $rating++;
You could also try using the array functions like sorting the values first and get keys of the sorted array and then create another array with the extracted keys as values. Now you get the same array with their rankings, except that you have '0' rank first as arrays start with an index 0.
May be you could pad an additional value with '0' an then finally remove it.
Something like this,
$total['A']=5;
$total['B']=7;
$total['C']=6;
$total[0]=0;
asort($total);
$total = array_slice(array_flip(array_keys($total)),1);
Or if you don't like to pad an extra value, you can try it this way. Create an array with the keys and the count of the sorted array.
asort($total);
$total = array_combine(array_keys($total),range(1, count($total)));
This might be a quick and easy way of doing. Hope this helps.
How to I get an array of the last n items of another array in PHP?
$n is equal to the number of items you want off the end.
$arr = array_slice($old_arr, -$n);
You can use array_slice:
$arr = array_slice($old_arr, -$n, $n, true);
If the array indices are meaningful to you, remember that array_slice will reset and reorder the numeric array indices. You need the preserve_keys flag (4th parameter) set to true to avoid this.