PHP Judy

PHP Judy - Extension for creating and accessing dynamic arrays

Table of Contents

1. Introduction
2. Directory Contents
3. Installation
4. Usage Examples
5. Reporting Bugs
6. Todo

Introduction

php-judy is an extension by Nicolas Brousse for the Judy C library. It is compatible with PHP 8.0 and newer.

• PECL Package: http://pecl.php.net/package/Judy
• Packagist Package: https://packagist.org/packages/orieg/judy
• GitHub Repository: http://github.com/orieg/php-judy

A Judy array is a complex but very fast associative array data structure for storing and looking up values using integer or string keys. Unlike normal arrays, Judy arrays may be sparse; that is, they may have large ranges of unassigned indices.

• Wikipedia: http://en.wikipedia.org/wiki/Judy_array

The PHP extension is based on the Judy C library that implements a dynamic array. A Judy array consumes memory only when populated yet can grow to take advantage of all available memory. Judy's key benefits are: scalability, performance, memory efficiency, and ease of use. Judy arrays are designed to grow without tuning into the peta-element range, scaling near O(log-base-256) -- 1 more RAM access at 256 X population.

• Judy C Library: http://judy.sourceforge.net

For a detailed performance comparison with native PHP arrays, please see the BENCHMARK.md file.

Directory Contents

README.md          This file
LICENSE           The PHP License used by this project
EXPERIMENTAL      Note about the status of this package
BENCHMARK.md      Performance benchmarks and analysis
MIGRATION_2.2.0.md Migration guide for version 2.2.0

lib/              Header and source libraries used by the package
libjudy/          Bundled libJudy
tests/            Unit tests
examples/         PHP test/example scripts
*.c, *.h          Header and source files used to build the package
*.php             PHP test/examples scripts

Installation

A. Using PHP PIE (Recommended)

PHP PIE (PHP Extension Installer) is the easiest way to install PHP Judy on supported platforms:

# Install PHP PIE if you don't have it
curl -sSL https://pie.dev/installer | php

# Install PHP Judy using PIE
pie install judy

Note: PHP PIE automatically handles dependencies and builds the extension for your specific PHP version and platform.

B. Using PECL

You can also install PHP Judy using PECL:

# Install the extension with pecl
pecl install judy

Note: You may need to install the Judy C library first on some systems.

C. Linux (Manual Build)

From the PHP Judy sources:

phpize
./configure --with-judy[=DIR]
make
make test
make install

If you are using Ubuntu or Debian, you can install libJudy with apt:

apt-get install libjudydebian1 libjudy-dev
phpize
./configure --with-judy=/usr
make
make test
make install

D. Windows

On Windows, you will need to build LibJudy yourself.

Download the sources at http://sourceforge.net/projects/judy/

Extract the sources, and open the Visual Studio command prompt and navigate to the source directory. Then execute:

build

This creates "Judy.lib", copy this into the php-sdk library folder and name it libJudy.lib

Then copy the include file "judy.h" into the php-sdk includes folder. Now it's time to build pecl/judy, extract the pecl/judy into your build folder where the build scripts will be able to pick it up, e.g.:

C:\php\pecl\judy\

If your source of PHP is located in:

C:\php\src\

The rest of the steps is pretty straightforward, like any other external extension:

buildconf
configure --with-judy=shared
nmake

E. Mac OS X

The recommended way to install php-judy on Mac OS X is by using pie or pecl. You will need to have the Judy C library installed first, which can be done easily with Homebrew.

Using PHP PIE (Recommended)

# Install PHP PIE if you don't have it
curl -sSL https://pie.dev/installer | php

# Install PHP Judy using PIE
pie install judy

Using PECL

# First, install the Judy C library
brew install judy

# Then, install the extension with pecl
pecl install judy

Manual Install

If you prefer to compile from source, you will need to install the libJudy first. Download the sources at http://sourceforge.net/projects/judy/

Extract the sources, then cd into the source directory and execute:

./configure
make
make install

Usage Examples

Judy arrays can be used like usual PHP arrays. The difference will be in the type of key/values that you can use. Judy arrays are optimized for memory usage but it forces some limitations in the PHP API.

There are currently 5 types of PHP Judy Arrays:

1. Judy::BITSET

A Judy array with only 1 bit per index. It can be used to store boolean values.

$judy = new Judy(Judy::BITSET);
$judy[100] = true;
$judy[200] = true;
$judy[300] = false;

if ($judy[100]) {
    echo "Index 100 is set\n";
}

2. Judy::INT_TO_INT

A Judy array with integer keys and integer values.

$judy = new Judy(Judy::INT_TO_INT);
$judy[1] = 100;
$judy[2] = 200;
$judy[3] = 300;

echo $judy[2]; // Outputs: 200

3. Judy::INT_TO_MIXED

A Judy array with integer keys and mixed values (strings, integers, etc.).

$judy = new Judy(Judy::INT_TO_MIXED);
$judy[1] = "Hello";
$judy[2] = 42;
$judy[3] = [1, 2, 3];

echo $judy[1]; // Outputs: Hello

4. Judy::STRING_TO_INT

A Judy array with string keys and integer values.

$judy = new Judy(Judy::STRING_TO_INT);
$judy["apple"] = 1;
$judy["banana"] = 2;
$judy["cherry"] = 3;

echo $judy["banana"]; // Outputs: 2

5. Judy::STRING_TO_MIXED

A Judy array with string keys and mixed values.

$judy = new Judy(Judy::STRING_TO_MIXED);
$judy["name"] = "John Doe";
$judy["age"] = 30;
$judy["scores"] = [85, 92, 78];

echo $judy["name"]; // Outputs: John Doe

Iterator Interface (PHP 8+)

Judy arrays implement the PHP Iterator interface, allowing you to use them in foreach loops:

$judy = new Judy(Judy::INT_TO_MIXED);
$judy[1] = "First";
$judy[5] = "Fifth";
$judy[10] = "Tenth";

// Iterate through all elements
foreach ($judy as $key => $value) {
    echo "Key: $key, Value: $value\n";
}

// Manual iteration
$judy->rewind();
while ($judy->valid()) {
    $key = $judy->key();
    $value = $judy->current();
    echo "Key: $key, Value: $value\n";
    $judy->next();
}

Performance Considerations

• Memory Efficiency: Judy arrays use 2-4x less memory than PHP arrays
• Sequential Access: Excellent performance for ordered iteration
• Range Queries: Native support for range operations
• Random Access: Slower than PHP arrays (O(log n) vs O(1))

For detailed performance analysis, see BENCHMARK.md.

Reporting Bugs

Please report bugs and issues on the GitHub repository:

https://github.com/orieg/php-judy/issues

Todo

• Additional performance optimizations
• More comprehensive test coverage
• Additional documentation and examples
• Integration with more PHP frameworks

License

This project is licensed under the PHP License - see the LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Support

• Documentation: BENCHMARK.md for performance analysis
• Migration Guide: MIGRATION_2.2.0.md for version 2.2.0 changes
• Examples: Check the examples/ directory for usage examples