How to randomize array from the range of indexes?

Question

I am currently working on room assigning, how do I randomize array from only indexes 1 to 3? I have 4 indexes in my array.

$arrayroom = array("1","2","3","4");
$check1 = "SELECT COUNT(*) AS Total FROM grade_7 WHERE Room_Number = '1' ";
    $ch= mysqli_query($conn,$check1);
    $d = mysqli_fetch_assoc($ch);
    if($d['Total'] < 40){
        $room = $arrayroom[0];
     }
     else{
        $room = array_rand($arrayroom);
     }

mighty_dev · Accepted Answer · 2019-12-07 14:29:12Z

1

You can split the array into two parts.
Shuffle the first part and keep the second part as is.
Merge both parts to get your result.

Snippet:

<?php

$input = array("Neo", "Morpheus", "Trinity", "Cypher", "Tank");

$randomize = array_slice($input,0,3);
$keep_safe = array_slice($input,3);
shuffle($randomize);
print_r(array_merge($randomize,$keep_safe));

Demo: https://3v4l.org/HVMc8

answered Dec 7, 2019 at 14:29

mighty_dev

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Aksen P · Accepted Answer · 2019-12-07 17:02:14Z

0

You can use this simple function for retrieving your desired output:

function arrayRangeRand(&$arr, $s, $e){
    $tmp = [];
    for($i=$s;$i<=$e;$i++){
        $tmp[] = $arr[$i];
    }
    shuffle($tmp);
    foreach($tmp as $ind=>$val){
        $arr[$s+$ind] = $val;
    }  
}

 arrayRangeRand($data, $firstInd, $lastInd0);

Demo

Here for loop collects values from-to, then shuffle them, and then replace old values with new ones with referred indexes. & mutates your original data array, so, you don't need to return anything.

answered Dec 7, 2019 at 17:02

Aksen P

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