How to implement repeated number statistics in arrays in PHP (code)

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All numbers in an array of length n are in the range of 0 to n-1. Some numbers in the array are repeated, but I don't know how many numbers are repeated. I don't know how many times each number is repeated. Please find any repeated number in the array. For example, if the input is an array {2,3,1,0,2,5,3} of length 7, then the corresponding output is the first repeated number 2.
1. Hash method
2. Define a backup array, used as a hash, the key is each element of the original array, the value is the number of occurrences
3. Traverse the hash array

hash
for i=0i;<arr.length;i++
    hash[arr[i]]++;
foreach hash as v
    return v

<?php
function duplicate($numbers, &$duplication)
{
    
    
    // write code here
    //这里要特别注意~找到任意重复的一个值并赋值到duplication[0]
    //函数返回True/False
        $flag=false;
        $hash=array();
        for($i=0;$i<count($numbers);$i++){
                $hash[$numbers[$i]]++;//关键
        }       
        foreach($hash as $k=>$v){
                if($v>=2){
                        $flag=true;
                        $duplication[0]=$k;
                        break;
                }
        }

        return $flag;
}
$arr=[2,1,3,0,4];
$res=duplicate($arr,$duplication);
var_dump($res);
var_dump($duplication);

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