The core methods of processing JSON data in PHP include using json_encode() and json_decode() functions. 1. When receiving JSON requests, get the original input through file_get_contents('php://input') and parse it into a PHP array or object with json_decode(); 2. When sending a JSON response, set the header('Content-Type: application/json'), and then use json_encode() to convert the data into JSON string output; 3. Always check encoding/decoding errors to ensure data integrity; 4. Avoid scripts output content in advance, keep the data types consistent, and pay attention to character set encoding issues. These steps can effectively ensure the correctness and stability of PHP and JSON in API interaction.

When you're working with PHP APIs, JSON is the go-to format for exchanging data because it's lightweight, easy to read, and widely supported. If you're building or consuming APIs in PHP, using JSON effectively comes down to understanding how to encode and decode it properly.

How PHP Handles JSON

PHP has built-in functions that make working with JSON straightforward: json_encode() and json_decode() . These are your main tools when sending or receiving data through an API.

• json_encode($data) takes a PHP array or object and converts it into a JSON string.
• json_decode($json, true) does the reverse — it parses a JSON string into a PHP array (when you set the second parameter to true ) or object if omitted.

A common example is receiving JSON from a POST request:

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

This line grabs raw input from an incoming HTTP request and turn it into a usable PHP array.

Sending JSON Responses from PHP

When your PHP script needs to return data as JSON (eg, from an API endpoint), you should first set the correct content type header:

 header('Content-Type: application/json');

Then, use json_encode() on your data and output it using echo :

 echo json_encode(['status' => 'success', 'data' => $result]);

Make sure to check if there's any error during encoding:

 if (json_last_error() === JSON_ERROR_NONE) {
    echo json_encode($response);
} else {
    http_response_code(500);
    echo json_encode(['error' => 'Failed to encode data']);
}

Also, be careful about what kind of data you're encoding — resources, circular references, or special characters can cause issues.

Handling JSON Requests to PHP APIs

If your PHP API is expecting to receive JSON data (like from a frontend app or another service), you need to read the raw input stream instead of relying on $_POST .

Here's how you typically do it:

• Use file_get_contents('php://input') to get the raw body of the request
• Pass that string into json_decode() to convert it into a PHP structure

You should always validate the decoded data before using it:

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

if (isset($input['username']) && !empty($input['username'])) {
    // process the username
} else {
    // respond with an error
}

Also, don't forget to send appropriate HTTP status codes when things go wrong, like 400 for bad requests or 415 if the content type isn't JSON.

A Few Things to Watch Out For

There are a few small but important details that can trip you up:

• Always check that json_encode() or json_decode() didn't run into errors using json_last_error()
• Make sure your PHP scripts don't output anything before sending JSON — even a space or notice will break it
• Be consistent with data types — eg, integers vs strings — especially when dealing with third-party services
• UTF-8 encoding matters — invalid characters can cause json_encode() to fail silently unless you handle them

For example, if you're pulling data from a database, make sure it's properly encoded before trying to turn it into JSON.

Basically that's it.

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