How to convert array into string in PHP - php

Question

I'm trying to convert an array in string in PHP so that I can store it into mySQL fields and reversely I can fetch:
Following is the data format:
array:2 [
0 => array:2 [
"year" => "234"
"amount" => "2387"
]
1 => array:2 [
"year" => "23"
"amount" => "324"
]
]
I'm trying something like this:
$var = implode(',', $data['revenues']);
I tried using implode but it is not working. Please help me out.
Edit
I tried this before:
public function store(Request $request)
{
$this->validate($request, Research::$create_validation_rules);
$data = $request->only(['coverage_date', 'company_id', 'contact_id', 'type', 'reco', 'target', 'projections', 'revenues', 'ebitas', 'profits']);
$data['coverage_date'] = Carbon::parse($request->coverage_date)->toDateTimeString();
$data['revenues'] = json_encode($data['revenues']);
$data['projections'] = json_encode($data['projections']);
$data['profits'] = json_encode($data['profits']);
$research = Research::create($data);
if($research)
{
return response()->json(['msg' => 'Successfully Created'], 200);
}
else
{
return response()->json(['msg' => 'Something went wrong'], 450);
}
}
Error which I'm getting is:

Answer 1

Use json_encode
example
$array = [["year" => "234","amount" => "2387"],["year" => "23","amount" => "324"]];
/*
Depending on PHP Version you can pass additional parameters
in json_encode for example json_encode($array,JSON_PRETTY_PRINT)
*/
$string = json_encode($array);
echo $string;
check this on PHP sandbox