Convert variable into array in php

When I use <pre>to display my variable echo $value_detail_final;
it displays a proper file like this

    {
        "companies": [
        {
        "id": "4127303000000527195",
        "company_name": "235 St Georges Landowning Trust & Australian City Properties Pty Ltd"
        },
        {
        "id": "4127303000004495043",
        "company_name": "Bourke Junction No 1 Pty Ltd"
        },
        {
        "id": "4127303000000527189",
        "company_name": "Brookfield Commercial Operations Pty Ltd"
        } 
       ]
    }

But when I use something like this $value_detail_final[0] it displays {
if $value_detail_final[1] its ", its like displaying each character on my variable .

even foreach doesnt work, by the way this is from json file and I use json_decode file.

How can I able to put each of the id and company_name into a variable so I can use them ?

This is how I decode my json file based on the given sturcture

$jsondata = file_get_contents("response.json");

$array = json_decode($jsondata,true);
echo "<pre>";
foreach ($array as $key => $value) {

    // echo "Key:".$key."<br>";
    if($key=='details')
    {
        foreach ($value as $key_detail => $detail)
        {

            if($key_detail=='userMessage')
            {
                foreach ($detail as $key_detail_final => $value_detail_final)
                {
                    print_r($value_detail_final);
                }
            }
        }
    }
}