Complete Guide to Looping Through JSON Data in PHP: Arrays, Objects, and Nested Structures

gitbox 2025-06-24

In modern web development, working with JSON data is a common task, and PHP remains one of the most widely used server-side scripting languages for such operations. JSON (JavaScript Object Notation) is known for its lightweight format and easy readability, making it ideal for data exchange.

This guide walks you through parsing and iterating over JSON data in PHP, demonstrating how to work with both arrays and objects, and offering a solution for nested data structures to improve your development workflow and code efficiency.

Parsing JSON Data

Before you can loop through JSON data, it must first be decoded into a PHP-compatible structure. PHP’s json_decode() function makes this easy:


$json = '{"name": "John", "age": 30, "city": "New York"}';
$data = json_decode($json, true); // Converts to an associative array

Setting the second parameter to true converts the JSON string into an associative array. If omitted or set to false, it converts the JSON into a PHP object instead.

Looping Through a JSON Array

Once the JSON data is converted into an array, you can easily loop through it using a foreach loop:


foreach ($data as $key => $value) {
    echo "$key: $value\n";
}

This snippet will output each key and its corresponding value. It’s simple and effective for flat data structures.

Looping Through a JSON Object

If the JSON is decoded as an object, the same looping approach applies, but now using object notation:


$json = '{"name": "John", "age": 30, "city": "New York"}';
$data = json_decode($json);

foreach ($data as $key => $value) {
    echo "$key: $value\n";
}

Both arrays and objects can be looped in similar ways; it just depends on how the JSON was decoded.

Handling Nested JSON Structures

Real-world JSON often comes in nested formats. In such cases, a recursive function is needed to loop through every level of the structure:


function traverse($data) {
    if (is_array($data) || is_object($data)) {
        foreach ($data as $key => $value) {
            if (is_array($value) || is_object($value)) {
                traverse($value); // Recursively handle nested values
            } else {
                echo "$key: $value\n";
            }
        }
    }
}

$json = '{"name": "John", "info": {"age": 30, "city": "New York"}}';
$data = json_decode($json);
traverse($data);

This function recursively visits each level of the JSON data, ensuring all values are accessed and output.

Conclusion

Looping through JSON in PHP is straightforward when you understand how json_decode works and how to use foreach with both arrays and objects. For more complex, nested JSON structures, recursion provides a clean and effective solution.

By mastering these techniques, you’ll be able to handle JSON data more efficiently in your PHP projects, resulting in cleaner and more maintainable code.

json_decode