Php and json data

How to extract and access JSON data in PHP

JavaScript Object Notation(JSON) is a lightweight human-readable text format for storing and transporting data consisting of name-value pairs and arrays.

It is easy to generate and parse in many programming languages. It is the most popular and lightweight data-interchange format for web applications and the de-facto format for the data exchange in RESTful web services requests and responses.

In this post, we will cover how to decode a JSON object and access its data in PHP.

Below is an example of a simple JSON object:

How to receive JSON data in PHP

1. From a POST or GET request

To receive JSON data as a POST request, we use the “php://input” along with the function file_get_contents() as below:

For instance, the JSON data is sent below as a POST request:

'; $curl = curl_init(); curl_setopt($curl, CURLOPT_URL, $url); curl_setopt($curl, CURLOPT_HTTPHEADER, array('Content-Type:application/json')); curl_setopt($curl, CURLOPT_RETURNTRANSFER, true); curl_setopt($curl, CURLOPT_POST, true); curl_setopt($curl, CURLOPT_POSTFIELDS, $payload); curl_exec($curl); curl_close($curl); 

To receive the above request data in the register.php file, just add file_get_contents(«php://input») and assign it to a variable for processing eg:

2. Reading a JSON file

A JSON file contains a JSON object and has a file extension of .json. You can as well open the file in PHP and access its data.

Similar to POST or GET request, we use file_get_contents() but instead of having “php://input”, we use the file path.

For example, if we have a JSON file with path «https://www.example.com/mydata.json«, we can access its data as below:

If the json file and the PHP file accessing it are in the same website, we can use relative path instead of the full file URL.

Extracting/Decoding JSON data in PHP

We use the built-in function json_decode() to convert the JSON string to the appropriate data type such as an object or an array.

1. Accessing JSON data as a PHP object

By default the json_decode() function returns an object.

Example
The example below decodes a JSON object into a PHP object:

'; $data = json_decode($json); var_dump($data); 

The above example outputs below:

object(stdClass)#1 (4) < ["firstName"]=>string(4) «John» [«lastName»]=> string(3) «Doe» [«email»]=> string(17) «johndoe@gmail.com» [«phone»]=> string(12) «111-111-1111» >

To access the PHP object data, you use the object operator (->) after the object name, followed by the key of the key-value pair. This is the same as the name in the name-value pair in JSON object eg $data->firstName .

'; $data = json_decode($json); echo "My name is".$data->firstName." ".$data->lastName; //Output: My name is John Doe 

2. Accessing JSON data as an array

You can as well convert the JSON object to a PHP associative array by passing a second(optional) parameter in the json_decode() function with the boolean value «true» as below. The value is set to false by default if you don’t pass it.

The example below decodes JSON object into a PHP associative array:

'; $data = json_decode($json, true); var_dump($data); 

The above example outputs below:

array(4) < ["firstName"]=>string(4) «John» [«lastName»]=> string(3) «Doe» [«email»]=> string(17) «johndoe@gmail.com» [«phone»]=> string(12) «111-111-1111» >

You access the data as in any other PHP associative array as in the example below:

'; $data = json_decode($json, true); echo "My name is ".$data["firstName"]." ".$data["lastName"]; //Output: My name is John Doe 

3. Accessing data in a nested JSON object

A JSON object may comprise of json objects and arrays as the values in its name-value pairs such as in the example below:

In the above example, the «address» has an object as its value while «siblings» has an array value comprising of objects.

The easiest way of accessing all the data is decoding the object as an associative array.

, "siblings": [ < "name": "Joseph Doe" >, < "name": "Mary Doe" >] >'; $data = json_decode($json, true); //Displaying all the data echo "First Name: ".$data["firstName"]."
"; //Output -> First Name: John echo "First Name: ".$data["lastName"]."
"; //Output -> Last Name: Doe echo "Email Address: ".$data["email"]."
"; //Output -> Email Address: johndoe@gmail.com echo "Postal Address: ".$data["address"]["postalAddress"]."
"; //Output -> Postal Address: 12345 echo "Postal Code: ".$data["address"]["postalCode"]."
"; //Output -> Postal Code: 5432 echo "City: ".$data["address"]["city"]."
"; //Output -> City: Nairobi echo "Sibling 1: ".$data["siblings"][0]["name"]."
"; //Output -> Sibling 1: Joseph Doe echo "Sibling 2: ".$data["siblings"][1]["name"]."
"; //Output -> Sibling 2: Mary Doe 

Looping through an object of objects with foreach()

You may have a large JSON object made of an array of objects, like in the example below:

To access the values of a country in the example above, you just have to know its object position in the array. For example, china is in the third position. But when accessing the array items, we start counting from 0, hence the index of China in the array is 2.

We access the China array object as below:

"; //Output -> Country: China echo "Code: ".$data["countries"][2]["code"]."
"; //Output -> Code: CN echo "City: ".$data["countries"][2]["city"]."
"; //Output -> City: Beijing 

If you want to access all the array data then it can be tiresome and time-consuming to write the code for accessing each at a time especially when the object is large. For such an instance, you can use the foreach() function to loop through all the objects as below:

, < "name": "India", "code": "IN", "city": "New Delhi" >, < "name": "China", "code": "CN", "city": "Beijing" >, < "name": "Germany", "code": "DE", "city": "Berlin" >, < "name": "Kenya", "code": "KE", "city": "Nairobi" >] >'; $countries = json_decode($json)->countries; foreach($countries as $country)< echo "Country: ".$country->name."
"; echo "Code: ".$country->code."
"; echo "City: ".$country->city."
"; > 

Conclusion

In this post, we have covered everything you need to know in extracting and accessing a JSON object data using PHP.

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PHP JSON

Summary: in this tutorial, you will learn how to convert data in PHP to JSON data and vice versa using the PHP JSON extension.

JSON stands for JavaScript Object Notation. JSON is designed as a lightweight data-interchange format.

JSON is built on two structures:

• A collection of name/value pairs called JSON objects. JSON objects are equivalent to associative arrays in PHP.
• An ordered list of values called arrays. They’re equivalent to indexed arrays in PHP.

The JSON format is human-readable and easy for computers to parse. Even though JSON syntax derives from JavaScript, it’s designed to be language-independent.

PHP JSON extension

PHP natively supports JSON via the JSON extension. The JSON extension provides you with some handy functions that convert data from PHP to JSON format and vice versa.

Since the JSON extension comes with PHP installation by default, you don’t need to do any extra configuration to make it works.

Converting PHP variables to JSON using json_encode() function

To get a JSON representation of a variable, you use the json_encode() function:

json_encode ( mixed $value , int $flags = 0 , int $depth = 512 ) : string|falseCode language: PHP (php)

The following example uses the json_encode() function to convert an indexed array in PHP to JSON format:

 $names = ['Alice', 'Bob', 'John']; $json_data = json_encode($names); // return JSON to the browsers header('Content-type:application/json'); echo $json_data;Code language: PHP (php)

• First, define an array of strings that consists of three elements.
• Second, convert the array to JSON using the json_encode() function.
• Third, return the JSON data to the browsers by setting the content type of the document to appplication/json using the header() function.

[ "Alice", "Bob", "John" ]Code language: JSON / JSON with Comments (json)

The following example uses the json_encode() function to convert an associative array in PHP to an object in JSON:

 $person = [ 'name' => 'Alice', 'age' => 20 ]; header('Content-type:application/json'); echo json_encode($person);Code language: PHP (php)

< name: "Alice", age: 20 >Code language: PHP (php)

In practice, you would select data from a database and use the json_encode() function to convert it to the JSON data.

Converting JSON data to PHP variables

To convert JSON data to a variable in PHP, you use the json_decode() function:

json_decode ( string $json , bool|null $associative = null , int $depth = 512 , int $flags = 0 ) : mixedCode language: PHP (php)

The following example shows how to use json_decode() function to convert JSON data to a variable in PHP:

 $json_data = ''; $person = json_decode($json_data); var_dump($person);Code language: PHP (php)

object(stdClass)#1 (2) ["name"] => string(5) "Alice" ["age"] => int(20) > Code language: PHP (php)

In this example, the json_decode() function converts an object in JSON to an object in PHP. The object is an instance of the stdClass class. To convert JSON data to an object of a specific class, you need to manually map the JSON key/value pairs to object properties. Or you can use a third-party package.

Serializing PHP objects

To serialize an object to JSON data, you need to implement the JsonSerializable interface. The JsonSerializable interface has the jsonSerialize() method that specifies the JSON representation of the object.

For example, the following shows how to implement the JsonSerializable interface and use the json_encode() function to serialize the object:

 class Person implements JsonSerializable < private $name; private $age; public function __construct(string $name, int $age) < $this->name = $name; $this->age = $age; > public function jsonSerialize() < return [ 'name' => $this->name, 'age' => $this->age ]; > > // serialize object to json $alice = new Person('Alice', 20); echo json_encode($alice);Code language: PHP (php)

"name":"Alice","age":20>Code language: PHP (php)

• First, define a Person class that implements the JsonSerializable interface.
• Second, return an array that consists of name and age properties from the jsonSerialize() method. The json_encode() function will use the return value of this method to create JSON data.
• Third, create a new Person object and serialize it to JSON data using the json_encode() function.

Summary

• JSON is a lightweight data-interchange format.
• Use the json_encode() function to convert PHP variables to JSON.
• Use the json_decode() function to convert JSON data to PHP variables.
• Implement the JsonSerializable interface to specify the JSON representation of an object.

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