PHP: Explain json_decode(file_get_contents("php://input"), true);

Statement

json_decode(file_get_contents("php://input"), true);

This line is commonly used in PHP APIs to read incoming JSON data from an HTTP request and convert it into a usable PHP array.

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1️⃣ php://input

php://input is a read-only stream that gives access to the raw body of the HTTP request.

It is used when:

• The request method is POST, PUT, PATCH, etc.

• The client sends JSON data (not form-data).

Example request body sent from frontend:

{
  "name": "Raju",
  "age": 25
}

php://input contains this raw JSON string.

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2️⃣ file_get_contents("php://input")

This function reads the raw request body as a string.

So this part:

file_get_contents("php://input")

returns:

'{"name":"Raju","age":25}'

It is still a string, not usable as an array.

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3️⃣ json_decode(..., true)

json_decode() converts JSON string into PHP data.

Syntax:

json_decode(string $json, bool $associative);

The second parameter:

• true → return associative array

• false (default) → return object

So:

$data = json_decode(file_get_contents("php://input"), true);

Now $data becomes:

[
  "name" => "Raju",
  "age" => 25
]

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4️⃣ Full Example API Usage

$data = json_decode(file_get_contents("php://input"), true);

$name = $data['name'];
$age = $data['age'];

echo "Name: $name, Age: $age";

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5️⃣ Why Not Use $_POST?

$_POST works only when:

• Content-Type: application/x-www-form-urlencoded

• Or multipart/form-data

If frontend sends:

Content-Type: application/json

Then $_POST will be empty.

That is why APIs use php://input.

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6️⃣ Best Practice (Safe Version)

Always check for errors:

$rawData = file_get_contents("php://input");
$data = json_decode($rawData, true);

if (json_last_error() !== JSON_ERROR_NONE) {
    http_response_code(400);
    echo json_encode(["error" => "Invalid JSON"]);
    exit;
}

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Summary

Part	Meaning
php://input	Raw HTTP request body
file_get_contents()	Reads the raw body
json_decode()	Converts JSON string to PHP data
true	Return associative array

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