PHP JSON

Working with JSON data in PHP

📦 What is PHP JSON?

JSON (JavaScript Object Notation) is a lightweight data format. PHP provides built-in functions to encode and decode JSON data, making it easy to exchange information between servers and web applications. 


<?php
// Simple JSON example
$data = array("name" => "John", "age" => 30);
echo json_encode($data);
?>

Output:

{"name":"John","age":30}

Key JSON Functions

📤

json_encode()

Convert PHP data to JSON format 

<?php
$arr = ["a", "b", "c"];
echo json_encode($arr);
?>
📥

json_decode()

Convert JSON to PHP data 

<?php
$json = '{"name":"Alice"}';
$obj = json_decode($json);
echo $obj->name;
?>
🔍

json_last_error()

Check for JSON errors 

<?php
json_decode("invalid");
if(json_last_error() != 0) {
    echo "Error!";
}
?>
✅

json_validate()

Validate JSON strings (PHP 8.3+) 

<?php
$valid = json_validate('{"a":1}');
echo $valid ? "Valid" : "Invalid";
?>

🔹 Encoding PHP Arrays to JSON

The json_encode() function converts PHP arrays and objects into JSON strings. This is useful when sending data to JavaScript or APIs. 

<?php
// Indexed array
$colors = array("red", "green", "blue");
echo json_encode($colors);

echo "\n\n";

// Associative array
$person = array(
    "name" => "Sarah",
    "age" => 25,
    "city" => "New York"
);
echo json_encode($person);
?>

Output:

["red","green","blue"]

{"name":"Sarah","age":25,"city":"New York"}

🔹 Decoding JSON to PHP

The json_decode() function converts JSON strings back into PHP variables. Use the second parameter to get an associative array instead of an object. 

<?php
$json = '{"name":"Mike","age":28,"skills":["PHP","MySQL"]}';

// Decode as object
$obj = json_decode($json);
echo "Name: " . $obj->name . "\n";
echo "Age: " . $obj->age . "\n";

echo "\n";

// Decode as array
$arr = json_decode($json, true);
echo "Name: " . $arr["name"] . "\n";
echo "Skills: " . implode(", ", $arr["skills"]);
?>

Output:

Name: Mike
Age: 28

Name: Mike
Skills: PHP, MySQL

🔹 JSON Encoding Options

PHP provides various options to format JSON output. These flags help make JSON more readable or handle special characters properly. 

<?php
$data = array(
    "name" => "José",
    "url" => "https://example.com/path",
    "price" => 19.99
);

// Pretty print
echo json_encode($data, JSON_PRETTY_PRINT);

echo "\n\n";

// Unescaped unicode and slashes
echo json_encode($data, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
?>

Output: 

{
    "name": "José",
    "url": "https://example.com/path",
    "price": 19.99
}
{"name":"José","url":"https://example.com/path","price":19.99}

🔹 Handling JSON Errors

Always check for errors when working with JSON. PHP provides functions to detect and handle JSON parsing errors gracefully. 

<?php
// Invalid JSON
$invalid_json = '{"name": "John", "age": }';

$result = json_decode($invalid_json);

if (json_last_error() !== JSON_ERROR_NONE) {
    echo "JSON Error: " . json_last_error_msg();
} else {
    echo "JSON is valid!";
}
?>

Output:

JSON Error: Syntax error

🔹 Working with Nested JSON

JSON can contain nested objects and arrays. PHP handles multi-level data structures easily with json_encode() and json_decode(). 

<?php
// Create nested structure
$company = array(
    "name" => "Tech Corp",
    "employees" => array(
        array("name" => "Alice", "role" => "Developer"),
        array("name" => "Bob", "role" => "Designer")
    )
);

$json = json_encode($company, JSON_PRETTY_PRINT);
echo $json;

echo "\n\n";

// Access nested data
$decoded = json_decode($json, true);
echo "First employee: " . $decoded["employees"][0]["name"];
?>

Output: 

{
    "name": "Tech Corp",
    "employees": [
        {"name": "Alice", "role": "Developer"},
        {"name": "Bob", "role": "Designer"}
    ]
}
First employee: Alice

🔹 Reading JSON from Files

You can read JSON data from external files and parse it into PHP. This is common when working with configuration files or data storage. 

<?php
// Read JSON file
$json_string = file_get_contents('data.json');
$data = json_decode($json_string, true);

// Access data
echo "Name: " . $data["name"];

// Write JSON to file
$new_data = array("status" => "active", "count" => 42);
file_put_contents('output.json', json_encode($new_data, JSON_PRETTY_PRINT));
?>

Common Use Cases:

  • API responses and requests
  • Configuration files
  • Data exchange between PHP and JavaScript
  • Storing structured data

🧠 Test Your Knowledge

Which function converts PHP arrays to JSON?