I made an anagram machine and I have an array of positive matches. The trouble is they are all in a different order, I want to be able to sort the array so the longest array values appear first.
Anybody have any ideas on how to do this?
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12 Answers
Use https://www.php.net/manual/en/function.usort.php
with this custom function
function sortByLength($a,$b){
return strlen($b)-strlen($a);
}
usort($array,'sortByLength');
Use uasort if you want to keep the old indexes, use usort if you don't care.
Also, I believe that my version is better because usort is an unstable sort.
$array = array("bbbbb", "dog", "cat", "aaa", "aaaa");
// mine
[0] => bbbbb
[1] => aaaa
[2] => aaa
[3] => cat
[4] => dog
// others
[0] => bbbbb
[1] => aaaa
[2] => dog
[3] => aaa
[4] => cat
8 Comments
Brian Kelly
This is good, though I wouldn't call the function just 'sort'. sortByLength below is more descriptive.
Jeffz
to all - remember about mb_strlen() - not all langs are same
fishbone
No Brian, the function's job is not to sort, but to compare. Therefore I would call it compareStrLengthNegatively
Don't Panic
Not naming it "sort" is important, not because of descriptiveness, but because of fatal error: cannot redeclare sort.
xZero
Why not use mb_strlen instead of strlen? Although slower than strlen, it will prevent headache once multi-byte value occurs.
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If you'd like to do it the PHP 5.3 way, you might want to create something like this:
usort($array, function($a, $b) {
return strlen($b) - strlen($a);
});
This way you won't pollute your global namespace.
But do this only if you need it at a single place in your source code to keep things DRY.
Comments
PHP7 is coming. In PHP7, you could use the Spaceship Operator.
usort($array, function($a, $b) {
return strlen($b) <=> strlen($a);
});
Hope this could help you in the future.
1 Comment
John
Interesting, didn't know about that one. I wonder if it has any performance benefit to just using a subtraction instead like @clttj suggested.
function sortByLength($a,$b){
if($a == $b) return 0;
return (strlen($a) > strlen($b) ? -1 : 1);
}
usort($array,'sortByLength');
5 Comments
Peter Bailey
There's a bug in this. Your equality condition is too narrow. The strings "abc" and "def" should return 0 from this sort, but won't. They will instead return 1. And while I realize that this isn't a grave error (the output won't look broken, it's technically inaccurate.
Thinker
'if($a == $b) return 0;' this is a mistake. We are talking about length.
Unknown
@ Peter and Thinker, yes its an oddity of the PHP manual. I myself did strlen($a) == strlen($b), but then I saw that since PHP uses an unstable sort, it doesn't matter! It still messes up the order. So I came up with the shortest function that works.
zalew
Had it from some example based on the manual (as unknown said), didn't really bother to analyse that as I'm not into php lately, just checked if it works. Got sth better - good.
zalew
Yep, the manual examples and comments sometimes are very sad, but I don't know if it's really worth giving a damn :) Cheerz.
Descending Order:
$array = ['aa', 'bb', 'c', 'ccc', 'a', 'ertre'];
usort($array, function($a, $b){
return strlen($a) < strlen($b);
});
var_export($array);
// Output
array (
0 => 'ertre',
1 => 'ccc',
2 => 'aa',
3 => 'bb',
4 => 'c',
5 => 'a',
)
Ascending Order:
$array = ['aa', 'bb', 'c', 'ccc', 'a', 'ertre'];
usort($array, function($a, $b){
return strlen($a) > strlen($b);
});
// Output
array (
0 => 'c',
1 => 'a',
2 => 'aa',
3 => 'bb',
4 => 'ccc',
5 => 'ertre',
)
1 Comment
mickmackusa
Why would anyone use this when the spaceship operator was recommended 5 years earlier on this page?
array_multisort(array_map('count', $arr), SORT_DESC, $arr);
Comments
Here is a snippet that demonstrates exactly why you should NOT use function calls inside of usort() -- you will be needlessly calling strlen() on values that were previously encountered.
In my 9-element array, array_multisort() calls strlen() 9 times, but usort() calls strlen() 23 times -- that's no bueno.
Code: (Demo)
function multisort($array) {
array_multisort(array_map('strlen', $array), SORT_DESC, $array);
printf(
"Total strlen() calls: %d\n%s\n---\n",
count($array),
var_export($array, true)
);
}
function usersort($array) {
usort(
$array,
function($a, $b) {
echo "strlen() called twice\n";
return strlen($b) <=> strlen($a);
}
);
var_export($array);
echo "\n---\n";
}
multisort($array);
usersort($array);
Output (from my own sample array):
Total strlen() calls: 9
array (
0 => 'eight',
1 => 'seven',
2 => 'three',
3 => 'five',
4 => 'four',
5 => 'nine',
6 => 'one',
7 => 'six',
8 => 'two',
)
---
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
strlen() called twice
array (
0 => 'three',
1 => 'seven',
2 => 'eight',
3 => 'four',
4 => 'five',
5 => 'nine',
6 => 'one',
7 => 'two',
8 => 'six',
)
---
Comments
Make an array of strlen of oyur array elements, and multisort it with your array.
foreach($Yourarray as $c=>$key) {
$key['maxlen'] = strlen($key);
$sort_numcie[] = $key['maxlen'];
}
array_multisort($sort_numcie, $Yourarray);
This will definately work. I am sure!
1 Comment
mickmackusa
Naming a value
$key is counterintuitive. Declaring associative element $key['maxlen'] immediately after declaring a scalar value as $key is just plain weird. $key['maxlen'] is frankly a useless variable declaration.In addition to the accepted answer, to sort an array by length with ascending OR descending order:
function strlen_compare($a,$b){
if(function_exists('mb_strlen')){
return mb_strlen($b) - mb_strlen($a);
}
else{
return strlen($b) - strlen($a);
}
}
function strlen_array_sort($array,$order='dsc'){
usort($array,'strlen_compare');
if($order=='asc'){
$array=array_reverse($array);
}
return $array;
}
Comments
Here's a way using the spaceship operator (needs PHP 7.0):
$arr = ['apple','pear','oranges','banana'];
usort($arr, function ($a, $b) { return (strlen($a) <=> strlen($b)); });
print_r($arr);
Comments
Here's a way I've done it in the past.
// Here's the sorting...
$array = array_combine($words, array_map('strlen', $words));
arsort($array);
1 Comment
Rudolf Pipopulo
array with same value will be combined: array("aba", "aa", "ad", "vcd", "aba");
It's simple.
function LSort(a,b){return a.length-b.length;}
var YourArray=[[1,2,3,4,5,6], ['a','b'], ['X','Y','Z'], ['I','Love','You'], ['good man']];
YourArray.sort(Lsort);
Result:
['good man'] Length=1
['a','b'] Length=3
['X','Y','Z'] Length=3
['I','Love','You'] Length=3
[1,2,3,4,5,6] Length=6
2 Comments
Gumbo
Please take a look at this Markdown help page to improve your formatting skills.
ericek111
This is not even PHP.