I have a code that will add a number to an array each time a page is visited. the numbers are stored in a cookie and are retrieved later.
I would like to keep only the 5 most recent numbers in the array.
if the array is full (5 items) and a new number must be added, then the oldest number must be removed and the most recent items must be kept
here's what i have:
$lastviewedarticles = array();
if (isset($_COOKIE["viewed_articles"]) ) {
$lastviewedarticles = unserialize($_COOKIE["viewed_articles"]);
}
if (!in_array($articleid, $lastviewedarticles)){
$lastviewedarticles[] = $articleid;
}
setcookie("viewed_articles", serialize($lastviewedarticles));
array_slice returns a slice of an array
array_slice($array, 0, 5) // return the first five elements
use array_splice and array_unique to get the 5 unique array values
array_splice(array_unique($lastviewedarticles), 0, 5);
First of all i think, you need to obtain array length , then if length > or equal to 5, remove first element , and add element to the end of array.
if (!in_array($articleid, $lastviewedarticles)){
$count = count($lastviewedarticles);
if($count>=5)
array_shift($lastviewedarticles);
$lastviewedarticles[] = $articleid;
}
Use a counter to access the array, increment it in every call and use the modulus operation to write into the array. If your counter has to persist over several calls you have to store it in a session variable or a cookie.
Assuming that $i holds your counter variable this would look like
if (!in_array($articleid, $lastviewedarticles)){
$lastviewedarticles[$i%5] = $articleid;
$i++;
}
The result is a primitive ring buffer that will always contain the last 5 values.
Related
Hey everyone I have a question about arrays and loops in PHP.
For a game I'm making, I need to write a function that generates a stack of crystal_id's based on a given size and ratio.
The ratio is the ratio between black crystals and different colored crystal (so a ratio of 0,25 (1:4) and a stack of 50 would yield a stack with 40 black crystals and 10 colored crystals).
I have all the math to calculate the amount of crystals per color and stuff figured out, but I can't figure out how to create an array with the right amount of colored crystals where each color is represented equally.
For reference, the array the code gets to choose from is a variable called $crystals_array, which is an array filled with integers where each integer represents a different colored crystal (e.g. [2,3,4,5,6]).
In the above case we have 5 different colored crystals and we needed a total of 10 colored crystals where each crystal is represented equally. So I need to create an array that looks a little something like this:
[2,2,3,3,4,4,5,5,6,6].
The code I have so far is this:
for($i = 0; $i <= count($amount_crystals_color) - 1; $i++)
{
$array = array_fill(0, $amount_crystals_per_color_stack, $crystals_array[$i]);
$i++;
}
Using the above example $amount_crystals_per_color_stack is equal to 2 and amount_crystals_color is equal to 5.
When executing this code it outputs an array: [2,2] which is how many 2's we need, but I can't figure out how to add the remaining crystals to this array.
Can anyone help me out?
Your code has several problems and i will address each of them individually.
Using the for loop to iterate over an array
You are using a for loop in your code, that has the following loop head:
for($i = 0; $i <= count($crystals_array) - 1; $i++)
The loop had consists of three parts, each separated by a semicolon (;).
The first part $i = 0 is the initialization part. Here you initialize a variable, that is later used as an iterator, which shall change in each loop iteration. You could name this the start point as well.
The second part $i <= count($crystals_array) - 1 is the condition part. A condition is formed, that shall express for how long the loop shall iterate. As long as the expression evaluates as true, the loop will run again. Therefore this condition is evaluated at the start of each iteration. As soon as the condition evaluates as false the loop will end. Therefore this part can be named endpoint as well.
The third part $i++ is the step size. This is executed at the end of each iteration and determines how the iterator (the variable you defined in the first part) shall change. $i++ is in this context equal to $i = $i + 1 and represents a step size of 1. Therefore the variable $i gets increased by 1 for each run of the loop.
This said, you can improve and fix your code regarding the for loop with two changes:
Save functions, that are executed in your condition part into an variable, if they return a constant result for each iteration. You use the count() function, which will then count your array again for each iteration of the for loop. By saving it in a variable $count = count($crystals_array); before the for loop and changing the condition to $i < $count, the function is only called once and your code gets faster.
Do not change the iterator variable $i outside of your loop header. This is really bad code style. You added the line $i++; to the end of your loop, but that is already done in the step size part of the for header. Because that is executed at the and of each iteration as well you increased the step size to two, meaning that you only run the for loop with $i = 0, $i = 2 and $i = 4 instead of for each element.
For your code the usage of the $i iterator is only to address the elements of the initial array. Even though you should understand the for loop for the future, you should use a foreach loop for this case instead. The following code would be equivalent to your for loop.
//This code still contains another major bug and is jsut a partial improvvement
foreach($crystals_array as $crystal) {
$array = array_fill(0, $amount_crystals_per_color_stack, $crystal);
}
As you can see, you neither need to worry about counting the initial array, nor in which index the current value is. Instead the variable $crystal will automatically contain the next element for each iteration.
Appending elements to an array
You used the following line to save the newly generated elements in your array:
$array = array_fill(0, $amount_crystals_per_color_stack, $crystal);
If you look closely, you use a standard assignment with $array = at the beginning of your line. This means, that (like with each variable assignment) the previous value of the variable gets overwritten by the new value provided from the right side of the assignment. What you do not want yet is to overwrite the array, but to append something to it.
This can be done by adding two squared brackets to the end of the variable name: $array[] = .... Now, if the variable $array is really an array, what ever value is on the right side of the assignment will be appended to the array, instead of overwriting it.
Managing result types the right way
The following line still contains a major problem:
$array[] = array_fill(0, $amount_crystals_per_color_stack, $crystal);
The result type of array_fill() is an array itself. By appending it to the previous array, you would get the following structure:
$array = [
[2, 2],
[3, 3],
[4, 4],
[5, 5],
[6, 6],
];
As you can see, the code did exactly what it should but not what you wanted. Each result (array) was appended to the array. The result is therefore an array or arrays (or a multidimensional array). What you want instead, is that the values of the result are appended to the existing array.
PHP offers a function for that, named array_merge(). This function takes all elements for one (or more) array(s) and appends them to the end of the first array, that was given to the function. You can use it as followed:
$newCrystals = array_fill(0, $amount_crystals_per_color_stack, $crystal);
$array = array_merge($array, $newCrystals);
As you can see the latter line contains a normal assignment again. ($array =) This is because array_merge() does not modify the first array given to it, but creates a new array with the merged fields. Therefore the new array contains all values from the old one and it is safe to overwrite the old one with it.
The complete code would therefore be:
$array = [];
foreach($crystals_array as $crystal) {
$newCrystals = array_fill(0, $amount_crystals_per_color_stack, $crystal);
$array = array_merge($array, $newCrystals);
}
As I understood the problem
$crystals_array = [2,3,4,5,6];
$amount_crystals_per_color_stack = 2;
$res = [];
foreach($crystals_array as $v) {
// repeat each item from array $amount_crystals_per_color_stack times
$res = array_merge($res, array_fill(0, $amount_crystals_per_color_stack, $v));
}
print_r($res); // [2,2,3,3,4,4,5,5,6,6]
You need to merge your array at each iteration of the loop (repl online) or you lose the result each time.
Like:
$array = array();
for($i = 0; $i < count($amount_crystals_color); $i++)
{
$array = array_merge($array, array_fill(0, $amount_crystals_per_color_stack, $crystals_array[$i]);
}
Also you don't need the $i++ in the loop, because it iterate twice otherwise, and you don't need count(..)-1 if the condition is < instead of <=.
You could use simple foreach() to achieve this-
$amount_crystals_per_color_stack = 2;
$array = [2,3,4,5,6];
$result = array();
foreach($array as $a){
for($i=1;$i<=$amount_crystals_per_color_stack;$i++){
array_push($result, $a);
}
}
print_r($result);
$players = array(
array('Lionel Messi', 'Luis Suarez', 'Neymar Jr'),
array('Ivan Rakitic', 'Andres Iniesta', 'Sergio Busquets'),
array('Gerrard Pique', 'Mascherano', 'Denis Suarez', 'Jordi Alba'),
array('MATS'),
array('Arda Turan', 'Munir El Hadadi', 'Umtiti')
);
Now i am trying to echo the number of all the elements within the boundary of this array $players. For example, there are 3 elements in the first, 3 in the second. There are 4 elements in the third, 1 element in the 4th and 3 elements in the last one. Altogether these elements are 14 elements. Now i want to display 'Total Players: 14'. I can show the number of categories (5) using count() function but can't count the total elements(14). I tried different approaches but couldn't succeed.
count() should be able to do this for you directly, using the COUNT_RECURSIVE flag:
$playerCount = count($players, COUNT_RECURSIVE) - count($players);
// $playerCount is now equal to 14
The subtraction of the normal count is because counting recursively adds the keys of the outer array in to the sum of elements, which just needs to be subtracted from the recursive count.
The native count() method can do that.
$count = count($players, COUNT_RECURSIVE) - count($players);
Because the recursive count will also count the number of $player groups you have, you have to subtract that number from the recursive count.
From the php documentation for count:
If the optional mode parameter is set to COUNT_RECURSIVE (or 1), count() will recursively count the array. This is particularly useful for counting all the elements of a multidimensional array.
One other way, pretty self-explanatory:
$count = array_sum(array_map('count', $players));
$count=0;
foreach($players as $row) $count+=count($row);
$count is now 14.
Live demo
You can use:
count($array, COUNT_RECURSIVE);
check count manual
Declare a variable initialised to 0 to accumulate the number of elements. Then, iterate the first array (which contains the other arrays), and for each element (which is also an array) use count() to obtain the number of elements and add that value to the accumulator variable.
$num_players = 0;
foreach($players as $row) {
$num_players += count($row);
}
I have a array that i want to select two item as random, And two keys are selected between the key 2 and the key 8.
$arr = array=(1,2,3,4,5,6,7,8,9,10,11,12);
I can get two random item:
$rand_keys = array_rand($arr, 2);
$arr[$rand_keys[0]]; // one
$arr[$rand_keys[0]]; // two
In the above code, It is possible that selected items be from the entire array. Now i want to know how can I limit my choice?
In fact i want to get random item from this array:
array=(2,3,4,5,6,7,8);
You can use array_slice to first take a part of the array before you take random items from it
$part = array_slice($arr, 1, 7); // outputs array(2,3,4,5,6,7,8)
So I make an API call. This generates an array with dynamic number of elements. I want to add additional empty keys until the number of elements reach 50 (api call will always be lesser than 50). What is the easiest way to do this? Currently I am doing:
$dataArray = $this->APICall();
$toAdd = 50 - count($dataArray);
for($x=$toAdd;$x<=50;$x++)
{
$dataArray[$x] = "";
}
I wanted to check if there is an easier, perhaps single-line way of doing this...
There is function array_fill that you can use to fill array with spaces to size of 50. And then merge it with initial array.
Documentation for array_fill is here
$dataArray = array_merge($dataArray, array_fill(count($dataArray), 50 - count($dataArray), ""));
Really struggling with this one:
I have an existing foreach, containing an if loop looking for specific values. But I also have an array containing values which if found should have the same action taken as the specific values:
Here I loop through and when values are between 5 and 9, I take the value of $datacolvalue and add it to another array as an integer rounded to 2 decimal places.
Otherwise, add it as a string, untouched.
$data_row = array();
$count = 1;
foreach ($row->COLUMN as $datacolvalue){
if($count > 4 && $count < 10)
$data_row[] = round((float)$datacolvalue, 2);
else
$data_row[] = (string)$datacolvalue;
$count++;
}
What I want to do, is is do the same thing $data_row[] = round((float)$datacolvalue, 2); if the value of $count is in a static array named $array_to_round which looks like this (values are different each time the php is run:
array(12,34,56,78);
I though about adding a foreach inside the "else" condition but I cannot get my head around it. Is a for/while/loop the answer?
In a nutshell, for each $datacolvalue, if $count is (> 4) and (< 10) OR is present in the $array_to_round array place in array as int and round, otherwise, place it as a string.
Use in_array to check if the value exists in the other array, then add it as necessary,
I would also store the rounded value if you plan to use it as a check and a setter.