I have an array for example
$a = [1,2,3,4,5];
From this $a, how to take last one and set it first like [5,1,2,3,4]
And how do I take last two arrays to make it like [4,5,1,2,3]
You can combine using array_pop(), which pops the last element of the array out, and array_unshift() to push it to the front of the array. You can create a simple function for this,
function array_pop_unshift($array) {
array_unshift($array, array_pop($array));
return $array;
}
Then use it as
$a = [1,2,3,4,5];
$new = array_pop_unshift($a);
print_r($new); // [5,1,2,3,4]
To continue shifting it, just call the function again until you're done, for instance through a for loop,
$a = [1,2,3,4,5];
for ($i = 0; $i < 2; $i++) {
$new = array_pop_unshift($a);
}
print_r($new); // [4,5,1,2,3]
Live demo at https://3v4l.org/CoJZZ
If you want to avoid the cost of several array_unshift and array_pop, you can build a generator that plays with the array internal pointer.
If you really need a result array, use iterator_to_array() to create it:
$a = range(1,5);
function rotate(&$array, $step = 1) {
$length = count($array);
end($array);
while ($step--)
prev($array);
while ($length--) {
next($array);
if (key($array) === null)
reset($array);
yield current($array);
}
}
print_r(iterator_to_array(rotate($a, 2))); // [4,5,1,2,3]
demo
Note that the rotate() generator uses a reference to avoid the array copy but doesn't modify the orginal array: it only moves the array pointer n times (where n is the array length) from the choosen position. When the array pointer is out of the array (key() returns null) the array pointer is reseted. In other words it stays efficient even with a large array and many rotations (what I have called "step" in the code).
You are actually doing right rotation, not left. Anyway, here are functions for doing both of them. They are probably not the most efficient but they are short in code and pretty self-explanatory:
<?php
function rotateLeft($array, $times) {
for($i=0; $i<$times; $i++){
$array[] = array_shift($array);
}
return $array;
}
function rotateRight($array, $times) {
for($i=0; $i<$times; $i++){
array_unshift($array, array_pop($array));
}
return $array;
}
$a = [1,2,3,4,5];
$a = rotateRight($a, 1);
print_r($a);
?>
to take last one and set it first This is known as right rotation.
And
$k is the number of units the shifting should be. $a is the array.
for($x=0; $x < $k; $x++){
//remove last element
$last = array_pop($a);
//push last element to the beginning
array_unshift($a, $last);
}
array_pop() pops and returns the value of the last element of array, shortening the array by one element.
https://www.php.net/manual/en/function.array-pop.php
array_unshift() prepends passed elements to the front of the array
https://www.php.net/manual/en/function.array-unshift.php
You could create a function that takes two arguments $k(number of rotations), $a (the array) and returns the array after performing right rotation $k times.
function rotateRight($a, $k){
for($x=0; $x < $k; $x++){
//remove last element
$last = array_pop($a);
//push last element to the beginning
array_unshift($a, $last);
}
return $a;
}
And then call it accordingly.
Example:
$a = [1,2,3,4,5];
$a_one_shift = rotateRight($a, 1);
// [5,1,2,3,4];
$a_two_shift = rotateRight($a_one_shift, 1);
// [4,5,1,2,3];
Or you could pass 2 to directly get the array after two right rotations.
$a_new = rotateRight($a, 2);
// [4,5,1,2,3];
Rather than making iterated calls of array_pop() and array_unshift(), use an efficient, elegant approach that makes fewer function calls and has the lowest possible time complexity. Using early returns prevents making needless function calls for the same result.
Code: (Demo)
function popUnshift(array $indexedArray, int $popShiftsCount): array
{
$count = count($indexedArray);
if ($count < 2) {
return $indexedArray; // array cannot be rotated
}
$remainder = $popShiftsCount % $count;
if (!$remainder) {
return $indexedArray; // sought rotation is the original order
}
return array_merge(
array_splice($indexedArray, -$remainder),
$indexedArray
);
}
Disclosure: This answer was built on the CodeReview page (Codility cyclic rotation solution in PHP) where I offered this snippet in my review.
//$A input array, $K rotation times
function solution($A, $K) {
$new = array();
for($j=1;$j<=$K;$j++)
{
if(count($new)>0)
$A = $new;
for($i=0;$i<count($A);$i++)
{
if($i==0)
$new[$i] = $A[count($A)-1];
else
$new[$i] = $A[$i-1];
}
}
return $new;}
say I have an array
$test_backwards=array("something1","something2","something3");
this is just a testing example and it's important to note that values will be added dinamically in my final array. so is it possible to dynamically return values from behind, namely starting from the last element?
something like this but backwards
for($i=0;$i<count($test_backwards);$i++) {
echo $test_backwards.'<br>';
}
Just start at the end and decrement your index:
for ($i = count($test_backwards) - 1; $i >= 0; $i--) {
echo $test_backwards[$i].'<br>';
}
or use array_reverse() (slower):
$test_backwards = array_reverse($test_backwards);
for ($i = 0; $i < count($test_backwards); $i++) {
echo $test_backwards[$i].'<br>';
}
You can also use array_pop(), if you do not need to keep this array. Or you can assign it to a temp array and then array_pop it, it will get and delete value from last.
$temp = $test_backwards;
while(($item = array_pop($temp)) !== NULL ) {
echo $item;
}
There is an array :
$ret = array();
... query execution
$ret['cnt'] = $this->db->num_rows(); // total number of database records
$i = 0;
while ( $this->db->next_record() ) { // fetching database records
$ret[$i]["user_id"] = $this->db->f('user_id') ;
$ret[$i]["user_login"] = stripslashes($this->db->f('user_login'));
$i++;
}
Now I want to remove from this array the element whose "user_id" is equal to a particular value :
if ($ret['cnt'] > 0) {
for ($i=0; $i<$ret['cnt']; $i++) {
if ($ret[$i]['user_id'] == $_SESSION[CODE_USER]) {
unset($ret[$i]);
break;
}
}
}
After printing the array I noticed that the element 0 is not in the array , this is what I am expecting. The only problem is now how to rearrange the array elements so that it will be compact again without any hole in its elements because the element 0 is not present ?
Use array_values:
$ret = array_values($ret);
http://php.net/manual/en/function.array-values.php
Or instead of using the 0th index. You could just grab the first element with reset.
http://php.net/manual/en/function.reset.php
array_values is probably the simplest way to reset keys.
if ($ret['cnt'] > 0) {
for ($i=0; $i<$ret['cnt']; $i++) {
if ($ret[$i]['user_id'] == $_SESSION[CODE_USER]) {
$ret = array_slice($ret,$i,1);
break;
}
}
}
array_slice will also strip away a section of the array and re-index as necessary.
I have a php array
How can I compare all values of this array and filter out values based on custom logic (callback function maybe).
Essentially, I want to compare each array value with every other value within the array and based on some custom logic, either keep the value or remove it from the array
Thanks
Probably you have to do it manually:
function your_callback($a, $b)
{
return $a != $b;
}
$array = array(/** Your array here... **/);
$n = count($array);
$filtered = array();
for($i = 0; $i < $n; $i++)
{
$ok = true;
for($j = 0; $j < $n; $j++)
{
if($j != $i && !your_callback($array[$i], $array[$j])
{
$ok = false;
break;
}
}
if($ok)
array_push($filtered, $array[$i]);
}
unset($array);
$array = $filtered;
This example will filter unique values of array for example; change your_callback definition to implement other logic.
You can call array_map, passing your callback as the first argument, and passing your array twice, as the second and the third argument. In the callback function, you loop through the "second" array and return the element if you want.
If you are looking to compare values of one array with values of another array in sequence then my code is really simple: check this out it will work like this:
if (1st value of array-1 is equal to 1st value of array-2) { $res=$res+5}
if($_POST){
$res=0;
$r=$_POST['Radio1']; //array-1
$anr=$_POST['answer']; //array-2
$arr=count($r);
for($ac=0; $ac<$arr; $ac++){
if($r[$ac]==$anr[$ac]){
$res=$res+5;
}
}
echo $res;
}
I have a database table with images that I need to display. In my view, I'd like to display UP TO 10 images for each result called up. I have set up an array with the 20 images that are available as a maximum for each result (some results will only have a few images, or even none at all). So I need a loop that tests to see if the array value is empty and if it is, to move onto the next value, until it gets 10 results, or it gets to the end of the array.
What I'm thinking I need to do is build myself a 2nd array out of the results of the test, and then use that array to execute a regular loop to display my images. Something like
<?php
$p=array($img1, $img2.....$img20);
for($i=0; $i<= count($p); $i++) {
if(!empty($i[$p])) {
...code
}
}
?>
How do I tell it to store the array values that aren't empty into a new array?
you could do something like:
$imgs = array(); $imgs_count = 0;
foreach ( $p as $img ) {
if ( !empty($img) ) {
$imgs[] = $img;
$imgs_count++;
}
if ( $imgs_count === 10 ) break;
}
You can simply call array_filter() to get only the non-empty elements from the array. array_filter() can take a callback function to determine what to remove, but in this case empty() will evaluate as FALSE and no callback is needed. Any value that evaluates empty() == TRUE will simply be removed.
$p=array($img1, $img2.....$img20);
$nonempty = array_filter($p);
// $nonempty contains only the non-empty elements.
// Now dow something with the non-empty array:
foreach ($nonempty as $value) {
something();
}
// Or use the first 10 values of $nonempty
// I don't like this solution much....
$i = 0;
foreach ($nonempty as $key=>$value) {
// do something with $nonempty[$key];
$i++;
if ($i >= 10) break;
}
// OR, it could be done with array_values() to make sequential array keys:
// This is a little nicer...
$nonempty = array_values($nonempty);
for ($i = 0; $i<10; $i++) {
// Bail out if we already read to the end...
if (!isset($nonempty[$i]) break;
// do something with $nonempty[$i]
}
$new_array[] = $p[$i];
Will store $p[$i] into the next element of $new_array (a.k.a array_push()).
Have you thought about limiting your results in the sql query?
select * from image where img != '' limit 10
This way you are always given up to 10 results that are not empty.
A ẁhile loop might be what you're looking for http://php.net/manual/en/control-structures.while.php