PHP Function to Convert Array to JSON

This article explains how to convert a PHP array into a JSON string using the built-in PHP function. You will learn the exact function to use, its syntax, practical code examples, and how to format the resulting JSON output.

The json_encode() Function

In PHP, the json_encode() function is used to convert an array (or an object) into a JSON string representation. This function is essential for sending data from a PHP backend to a JavaScript frontend, API endpoints, or mobile applications.

Basic Syntax

json_encode(mixed $value, int $flags = 0, int $depth = 512): string|false

• $value: The value being encoded. This is typically an associative or indexed array.
• $flags: Optional bitmask constants that modify the encoding behavior (e.g., formatting).
• $depth: Optional maximum depth. Must be greater than zero.
• Return Value: Returns a JSON-encoded string on success, or false on failure.

Code Examples

1. Converting an Associative Array

An associative array in PHP converts into a JSON object.

<?php
// Define an associative array
$user = [
    "name" => "John Doe",
    "email" => "john@example.com",
    "age" => 30,
    "isAdmin" => true
];

// Convert array to JSON string
$jsonString = json_encode($user);

// Output the JSON string
echo $jsonString;
?>

Output:

{"name":"John Doe","email":"john@example.com","age":30,"isAdmin":true}

2. Converting an Indexed Array

A simple indexed array in PHP converts into a JSON array.

<?php
// Define an indexed array
$colors = ["red", "green", "blue"];

// Convert array to JSON string
$jsonString = json_encode($colors);

echo $jsonString;
?>

Output:

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

Useful Flags for json_encode()

You can pass specific constants as the second argument to customize the JSON string output:

• JSON_PRETTY_PRINT: Uses whitespace to format the returned data for human readability.
• JSON_UNESCAPED_SLASHES: Prevents PHP from escaping forward slashes (/).
• JSON_NUMERIC_CHECK: Encodes numeric strings as numbers instead of strings.

Example with Flags:

<?php
$data = [
    "url" => "https://example.com/api",
    "status" => "200"
];

// Use flags to pretty print and prevent escaped slashes
$jsonString = json_encode($data, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_NUMERIC_CHECK);

echo $jsonString;
?>

Output:

{
    "url": "https://example.com/api",
    "status": 200
}