How to get the last n items in a PHP array as another array?
$n is equal to the number of items you want off the end.
$arr = array_slice($old_arr, -$n);
PHP get the last 3 elements of an associative array while preserving the keys?
If you want to preserve key, you can pass in true as the fourth argument:
array_slice($a, -3, 3, true);
Getting last 5 elements of a php array
You need array_slice, which does exactly this.
$items = array_slice($items, -5);
-5 means "start at five elements before the end of the array".
How to get the last element of an array without deleting it?
The many answers in this thread present us with many different options. To be able to choose from them I needed to understand their behavior and performance. In this answer I will share my findings with you, benchmarked against PHP versions 5.6.38, 7.2.10 and 7.3.0RC1 (expected Dec 13 2018).
The options (<<option code>>s) I will test are:
- option .1.
$x = array_values(array_slice($array, -1))[0];(as suggested by rolacja) - option .2.
$x = array_slice($array, -1)[0];(as suggested by Stoutie) - option .3.
$x = array_pop((array_slice($array, -1)));(as suggested by rolacja) - option .4.
$x = array_pop((array_slice($array, -1, 1)));(as suggested by Westy92) - option .5.
$x = end($array); reset($array);(as suggested by Iznogood) - option .6.
$x = end((array_values($array)));(as suggested by TecBrat) - option .7.
$x = $array[count($array)-1];(as suggested by Mirko Pagliai) - option .8.
$keys = array_keys($array); $x = $array[$keys[count($keys)-1]];(as suggested by thrau) - option .9.
$x = $array[] = array_pop($array);(as suggested by user2782001) - option 10.
$x = $array[array_key_last($array)];(as suggested by Quasimodo's clone ; available per PHP 7.3)
(functions mentioned: array_key_last , array_keys , array_pop , array_slice , array_values , count , end , reset)
The test inputs (<<input code>>s) to combine with:
- null =
$array = null; - empty =
$array = []; - last_null =
$array = ["a","b","c",null]; - auto_idx =
$array = ["a","b","c","d"]; - shuffle =
$array = []; $array[1] = "a"; $array[2] = "b"; $array[0] = "c"; - 100 =
$array = []; for($i=0;$i<100;$i++) { $array[] = $i; } - 100000 =
$array = []; for($i=0;$i<100000;$i++) { $array[] = $i; }
For testing I will use the 5.6.38, 7.2.10 and 7.3.0RC1 PHP docker containers like:
sudo docker run -it --rm php:5.6.38-cli-stretch php -r '<<<CODE HERE>>>'
Each combination of the above listed <<option code>>s and <<input code>>s will be run on all versions of PHP. For each test run the following code snippet is used:
<<input code>> error_reporting(E_ALL); <<option code>> error_reporting(0); $before=microtime(TRUE); for($i=0;$i<100;$i++){echo ".";for($j=0;$j<100;$j++){ <<option code>> }}; $after=microtime(TRUE); echo "\n"; var_dump($x); echo round(($after-$before)/(100*100)*1000*1000*1000);
For each run this will var_dump the last retrieved last value of the test input and print the average duration of one iteration in femtoseconds (0.000000000000001th of a second).
The results are as follows:
/==========================================================================================================================================================================================================================================================================================================================================================================================================================\
|| || T E S T I N P U T - 5 . 6 . 3 8 || T E S T I N P U T - 7 . 2 . 1 0 || T E S T I N P U T - 7 . 3 . 0 R C 1 ||
|| || null | empty | last_null | auto_idx | shuffle | 100 | 100000 || null | empty | last_null | auto_idx | shuffle | 100 | 100000 || null | empty | last_null | auto_idx | shuffle | 100 | 100000 ||
||============================OPTIONS - ERRORS==========================++===============+===============+===============+===============+===============+===============+===============++===============+===============+===============+===============+===============+===============+===============++===============+===============+===============+===============+===============+===============+===============<|
|| 1. $x = array_values(array_slice($array, -1))[0]; || W1 + W2 | N1 | - | - | - | - | - || W1 + W2 | N1 | - | - | - | - | - || W1 + W2 | N1 | - | - | - | - | - ||
|| 2. $x = array_slice($array, -1)[0]; || W1 | N1 | - | - | - | - | - || W1 | N1 | - | - | - | - | - || W1 | N1 | - | - | - | - | - ||
|| 3. $x = array_pop((array_slice($array, -1))); || W1 + W3 | - | - | - | - | - | - || W1 + N2 + W3 | N2 | N2 | N2 | N2 | N2 | N2 || W1 + N2 + W3 | N2 | N2 | N2 | N2 | N2 | N2 ||
|| 4. $x = array_pop((array_slice($array, -1, 1))); || W1 + W3 | - | - | - | - | - | - || W1 + N2 + W3 | N2 | N2 | N2 | N2 | N2 | N2 || W1 + N2 + W3 | N2 | N2 | N2 | N2 | N2 | N2 ||
|| 5. $x = end($array); reset($array); || W4 + W5 | - | - | - | - | - | - || W4 + W5 | N2 | N2 | N2 | N2 | N2 | N2 || W4 + W5 | - | - | - | - | - | - ||
|| 6. $x = end((array_values($array))); || W2 + W4 | - | - | - | - | - | - || W2 + N2 + W4 | - | - | - | - | - | - || W2 + N2 + W4 | N2 | N2 | N2 | N2 | N2 | N2 ||
|| 7. $x = $array[count($array)-1]; || - | N3 | - | - | - | - | - || W7 | N3 | - | - | - | - | - || W7 | N3 | - | - | - | - | - ||
|| 8. $keys = array_keys($array); $x = $array[$keys[count($keys)-1]]; || W6 | N3 + N4 | - | - | - | - | - || W6 + W7 | N3 + N4 | - | - | - | - | - || W6 + W7 | N3 + N4 | - | - | - | - | - ||
|| 9. $x = $array[] = array_pop($array); || W3 | - | - | - | - | - | - || W3 | - | - | - | - | - | - || W3 | - | - | - | - | - | - ||
|| 10. $x = $array[array_key_last($array)]; || F1 | F1 | F1 | F1 | F1 | F1 | F1 || F2 | F2 | F2 | F2 | F2 | F2 | F2 || W8 | N4 | F2 | F2 | F2 | F2 | F2 ||
||========================OPTIONS - VALUE RETRIEVED=====================++===============+===============+===============+===============+===============+===============+===============++===============+===============+===============+===============+===============+===============+===============++===============+===============+===============+===============+===============+===============+===============<|
|| 1. $x = array_values(array_slice($array, -1))[0]; || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) ||
|| 2. $x = array_slice($array, -1)[0]; || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) ||
|| 3. $x = array_pop((array_slice($array, -1))); || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) ||
|| 4. $x = array_pop((array_slice($array, -1, 1))); || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) ||
|| 5. $x = end($array); reset($array); || NULL | bool(false) | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | bool(false) | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | bool(false) | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) ||
|| 6. $x = end((array_values($array))); || NULL | bool(false) | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | bool(false) | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | bool(false) | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) ||
|| 7. $x = $array[count($array)-1]; || NULL | NULL | NULL | string(1) "d" | string(1) "b" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "b" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "b" | int(99) | int(99999) ||
|| 8. $keys = array_keys($array); $x = $array[$keys[count($keys)-1]]; || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) ||
|| 9. $x = $array[] = array_pop($array); || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) || NULL | NULL | NULL | string(1) "d" | string(1) "c" | int(99) | int(99999) ||
|| 10. $x = $array[array_key_last($array)]; || N/A | N/A | N/A | N/A | N/A | N/A | N/A || N/A | N/A | N/A | N/A | N/A | N/A | N/A || N/A | N/A | N/A | N/A | N/A | N/A | N/A ||
||=================OPTIONS - FEMTOSECONDS PER ITERATION=================++===============+===============+===============+===============+===============+===============+===============++===============+===============+===============+===============+===============+===============+===============++===============+===============+===============+===============+===============+===============+===============<|
|| 1. $x = array_values(array_slice($array, -1))[0]; || 803 | 466 | 390 | 384 | 373 | 764 | 1.046.642 || 691 | 252 | 101 | 128 | 93 | 170 | 89.028 || 695 | 235 | 90 | 97 | 95 | 188 | 87.991 ||
|| 2. $x = array_slice($array, -1)[0]; || 414 | 349 | 252 | 248 | 246 | 604 | 1.038.074 || 373 | 249 | 85 | 91 | 90 | 164 | 90.750 || 367 | 224 | 78 | 85 | 80 | 155 | 86.141 ||
|| 3. $x = array_pop((array_slice($array, -1))); || 724 | 228 | 323 | 318 | 350 | 673 | 1.042.263 || 988 | 285 | 309 | 317 | 331 | 401 | 88.363 || 877 | 266 | 298 | 300 | 326 | 403 | 87.279 ||
|| 4. $x = array_pop((array_slice($array, -1, 1))); || 734 | 266 | 358 | 356 | 349 | 699 | 1.050.101 || 887 | 288 | 316 | 322 | 314 | 408 | 88.402 || 935 | 268 | 335 | 315 | 313 | 403 | 86.445 ||
|| 5. $x = end($array); reset($array); || 715 | 186 | 185 | 180 | 176 | 185 | 172 || 674 | 73 | 69 | 70 | 66 | 65 | 70 || 693 | 65 | 85 | 74 | 68 | 70 | 69 ||
|| 6. $x = end((array_values($array))); || 877 | 205 | 320 | 337 | 304 | 2.901 | 7.921.860 || 948 | 300 | 336 | 308 | 309 | 509 | 29.696.951 || 946 | 262 | 301 | 309 | 302 | 499 | 29.234.928 ||
|| 7. $x = $array[count($array)-1]; || 123 | 300 | 137 | 139 | 143 | 140 | 144 || 312 | 218 | 48 | 53 | 45 | 47 | 51 || 296 | 217 | 46 | 44 | 53 | 53 | 55 ||
|| 8. $keys = array_keys($array); $x = $array[$keys[count($keys)-1]]; || 494 | 593 | 418 | 435 | 399 | 3.873 | 12.199.450 || 665 | 407 | 103 | 109 | 114 | 431 | 30.053.730 || 647 | 445 | 91 | 95 | 96 | 419 | 30.718.586 ||
|| 9. $x = $array[] = array_pop($array); || 186 | 178 | 175 | 188 | 180 | 181 | 186 || 83 | 78 | 75 | 71 | 74 | 69 | 83 || 71 | 64 | 70 | 64 | 68 | 69 | 81 ||
|| 10. $x = $array[array_key_last($array)]; || N/A | N/A | N/A | N/A | N/A | N/A | N/A || N/A | N/A | N/A | N/A | N/A | N/A | N/A || 370 | 223 | 49 | 52 | 61 | 57 | 52 ||
\=========================================================================================================================================================================================================================================================================================================================================================================================================================/
The above mentioned Fatal, Warning and Notice codes translate as:
F1 = Fatal error: Call to undefined function array_key_last() in Command line code on line 1
F2 = Fatal error: Uncaught Error: Call to undefined function array_key_last() in Command line code:1
W1 = Warning: array_slice() expects parameter 1 to be array, null given in Command line code on line 1
W2 = Warning: array_values() expects parameter 1 to be array, null given in Command line code on line 1
W3 = Warning: array_pop() expects parameter 1 to be array, null given in Command line code on line 1
W4 = Warning: end() expects parameter 1 to be array, null given in Command line code on line 1
W5 = Warning: reset() expects parameter 1 to be array, null given in Command line code on line 1
W6 = Warning: array_keys() expects parameter 1 to be array, null given in Command line code on line 1
W7 = Warning: count(): Parameter must be an array or an object that implements Countable in Command line code on line 1
W8 = Warning: array_key_last() expects parameter 1 to be array, null given in Command line code on line 1
N1 = Notice: Undefined offset: 0 in Command line code on line 1
N2 = Notice: Only variables should be passed by reference in Command line code on line 1
N3 = Notice: Undefined offset: -1 in Command line code on line 1
N4 = Notice: Undefined index: in Command line code on line 1
Based on this output I draw the following conclusions:
- newer versions of PHP perform better with the exception of these options that became significantly slower:
- option .6.
$x = end((array_values($array))); - option .8.
$keys = array_keys($array); $x = $array[$keys[count($keys)-1]];
- option .6.
- these options scale best for very large arrays:
- option .5.
$x = end($array); reset($array); - option .7.
$x = $array[count($array)-1]; - option .9.
$x = $array[] = array_pop($array); - option 10.
$x = $array[array_key_last($array)];(since PHP 7.3)
- option .5.
- these options should only be used for auto-indexed arrays:
- option .7.
$x = $array[count($array)-1];(due to use ofcount) - option .9.
$x = $array[] = array_pop($array);(due to assigning value losing original key)
- option .7.
- this option does not preserve the array's internal pointer
- option .5.
$x = end($array); reset($array);
- option .5.
- this option is an attempt to modify option .5. to preserve the array's internal pointer (but sadly it does not scale well for very large arrays)
- option .6.
$x = end((array_values($array)));
- option .6.
- the new
array_key_lastfunction seems to have none of the above mentioned limitations with the exception of still being an RC at the time of this writing (so use the RC or await it's release Dec 2018):- option 10.
$x = $array[array_key_last($array)];(since PHP 7.3)
- option 10.
A bit depending on whether using the array as stack or as queue you can make variations on option 9.
php: How to get the second-to-last element of an array?
You can use array_slice() like this:
<?php
$arr=['a','m','q','y','b','f','n','s'];
echo array_slice($arr, -2, 1)[0];
Output:
n
Note: this will work regardless of the array type: indexed or associative. So even if the keys are not 0, 1, 2, 3, etc... then this would still work.
Sort nested array using another array with PHP
You can flip the first array in order to know what's the order of the id's:
$order = array_flip($order);
Then you simply use usort to sort the array based on the earlier flipped array:
usort($array, static function(array $a, array $b) use ($order) {
return $order[$a['nr']] <=> $order[$b['nr']];
});
Extracting last n elements from array without disturbing original array
Use slice() instead of splice():
As from Docs:
The
slice()method returns a shallow copy of a portion of an array into a new array object selected from begin to end (end not included). The original array will not be modified.
var arr = [22, 55, 77, 88, 99, 22, 33, 44] ;
var newArr = arr.slice(-2);
console.log(newArr);console.log(arr);.as-console-wrapper { max-height: 100% !important; top: 0; }Echo only last 10 values of array
You can use array_slice(); for this.
Here an example:
<?php
$bidding_history_new = array_slice($bidding_history, -10);
foreach($bidding_history_new as $kk => $bhistory){
//whatever you do here
}
?>
More info about PHP's array_slice(); function: http://php.net/manual/en/function.array-slice.php
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