PHP - Why doesn't array_multisort function sort correctly?

Question

please view the following code with 2 arrays. i use multisort function with sort flags for ascending and numeric then display. as you can see in the output that array 2 starts with 100 when it should be last. please explain what is causing this and how to sort it correctly. thank you.

<?php 
$array1 = array(1,7,10,6);
$array2 = array(100,20,25,10);
array_multisort($array1, SORT_ASC, SORT_NUMERIC, $array2);
print_r($array1);  
echo "<br>";  
print_r($array2);  
?>

output:
Array ( [0] => 1 [1] => 6 [2] => 7 [3] => 10 )
Array ( [0] => 100 [1] => 10 [2] => 20 [3] => 25 )

zaf · Accepted Answer · 2016-05-30 15:04:02Z

2

Ah, yes, array_multisort is a bit tricky to understand the first time round.

Basically the sort is lexicographical, a fancy word meaning that the first array is sorted and the second arrays elements are ordered according to the first array.

Look at your first (output) array and see the order and map it to the initial second array and you'll see whats happening.

So the second array you take the 1st, 4th , 2nd and 3rd elements.

If you just want plain sorting for multiple arrays then just do them one by one or over a loop.

answered May 30, 2016 at 15:04

zaf

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