PHP How to Convert JSON to Array Easily

Use json_decode($jsonString, true) to convert a JSON string into a PHP array; the second parameter true makes the output an array instead of an object.

Examples

Input{"name":"John"}

OutputArray ( [name] => John )

Input[1,2,3]

OutputArray ( [0] => 1 [1] => 2 [2] => 3 )

Inputnull

OutputNULL

How to Think About It

To convert JSON to an array in PHP, you need to decode the JSON string. The function json_decode reads the JSON text and turns it into a PHP value. By default, it creates objects, but if you want an array, you set the second argument to true.

Algorithm

1

Get the JSON string input.

2

Call the JSON decoding function with the input and set the second parameter to true.

3

Store the result as a PHP array.

4

Use or return the array as needed.

Code

php

<?php
$jsonString = '{"name":"John", "age":30}';
$array = json_decode($jsonString, true);
print_r($array);
?>

Output

Array
(
    [name] => John
    [age] => 30
)

Dry Run

Let's trace converting '{"name":"John", "age":30}' to an array.

1

Input JSON string

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

2

Call json_decode with true

json_decode('{"name":"John", "age":30}', true)

3

Resulting PHP array

Array ( [name] => John [age] => 30 )

Step	Action	Value
1	Input JSON	{"name":"John", "age":30}
2	Decode JSON to array	Array ( [name] => John [age] => 30 )

Why This Works

Step 1: json_decode function

The json_decode function reads a JSON string and converts it into a PHP variable.

Step 2: Second parameter true

Passing true as the second argument tells PHP to convert JSON objects into associative arrays instead of PHP objects.

Step 3: Result is PHP array

The output is a PHP array that you can use like any other array in your code.

Alternative Approaches

Convert JSON to object

php

<?php
$jsonString = '{"name":"John", "age":30}';
$object = json_decode($jsonString);
print_r($object);
?>

This returns a PHP object instead of an array, which might be easier for some uses but less flexible for array functions.

Manually parse JSON (not recommended)

php

<?php
// Not recommended: manual parsing is error-prone and complex
$jsonString = '{"name":"John"}';
$array = []; // manual parsing would be complex
?>

Manual parsing is complicated and error-prone; always prefer json_decode.

Complexity: O(n) time, O(n) space

Time Complexity

The time depends on the length of the JSON string, as the function parses each character once.

Space Complexity

The space used grows with the size of the JSON string because it creates a new PHP array in memory.

Which Approach is Fastest?

Using json_decode with the second parameter is the fastest and most reliable way to convert JSON to an array.

Approach	Time	Space	Best For
json_decode with true	O(n)	O(n)	Converting JSON to array efficiently
json_decode default (object)	O(n)	O(n)	When PHP objects are preferred
Manual parsing	O(n^2) or worse	O(n)	Avoid due to complexity and errors