Essentials of LDAP with PHP

Need a straightforward method for storing address book-style data and network information alongside any structured data? LDAP, a technology dating back to 1993, provides a solution. While lacking the "cool" factor of newer technologies like Node.js and Go, its capabilities remain highly relevant.

Key Concepts:

• LDAP (Lightweight Directory Access Protocol), created at the University of Michigan in 1993, is an internet protocol for managing directory services. It efficiently stores and manages address book information, network details, and other organized data.
• OpenLDAP, a widely used open-source LDAP server, is schema-agnostic, meaning it doesn't impose restrictions on the data structure or content. It's easily installed and configured on Debian-based systems using command-line instructions.
• PHP interacts with LDAP servers via the Zend-Ldap component (from Zend Framework 2). This allows for server queries, connection management, and fundamental operations like database searches, entry updates, and deletions.
• LDAP directories employ a hierarchical tree-like structure, with the top level called the root or base. Each entry comprises attributes—each with a type and one or more values.

Understanding LDAP:

LDAP, or Lightweight Directory Access Protocol, originated at the University of Michigan around 1993, thanks to the efforts of Tim Howes, Steve Kille, Colin Robbins, and Wengyik Yeong. It's essentially an internet-friendly version of the older X.500 protocol (from the 1980s), originally designed by the International Telecommunications Union (ITU) for managing telephone directories.

While "LDAP" technically refers to the protocol, it's often used to describe both client and server components. Think of it as the SQL of directory servers—the language for interacting with LDAP-enabled servers.

Popular LDAP servers include Microsoft's Active Directory (integrated into Windows since Windows 2000) and the open-source OpenLDAP, which we'll use in this tutorial series. OpenLDAP's flexibility allows for diverse schema and data storage.

This first part covers:

1. OpenLDAP setup basics.
2. Loading data records.
3. Connecting and performing basic operations using PHP.

Essential Terminology:

Before proceeding, let's clarify some key terms:

LDAP Term	Description
dn	Distinguished Name: A record's unique identifier, similar to a primary key in relational databases.
Directory Schema	Defines the structure and constraints of the directory information.
entry	A record containing attributes that store data.
attribute	Similar to an associative array element or database column; specifies the data type, sorting rules, case-sensitivity, and other criteria.
cn	Common Name (e.g., "John Smith")
sn	Surname (e.g., "Smith")

For deeper understanding, consult O'Reilly's LDAP guides or the Wikipedia entry on LDAP.

Setting Up an LDAP Server:

OpenLDAP installation and configuration can be somewhat complex. These steps, optimized for Debian-based servers, aim for clarity and conciseness:

1. Install the core server and utilities:

   sudo apt-get install slapd ldap-utils

2. Configure the server:

   dpkg-reconfigure slapd

   Answer the prompts as follows:

   • Omit OpenLDAP server configuration? No
   • DNS domain name: homestead.localdomain (or your domain)
   • Name of your organization: (Your Organization Name)
   • Admin Password: (Choose a strong password)
   • Confirm Password: (Repeat the password)
   • OK
   • BDB (Berkeley DB)
   • Do you want your database to be removed when slapd is purged? No
   • Move old database? Yes
   • Allow LDAPv2 Protocol? No

Verification:

Check the installation by running:

ldapsearch -x -b dc=homestead,dc=localdomain

If you encounter errors, ensure OpenLDAP is running:

sudo netstat -tlnp | grep slapd

You should see output indicating slapd is listening on port 389.

Populating the Database:

Create users.ldif with the following content:

dn: cn=Sheldon Cooper,ou=People,dc=homestead,dc=localdomain
cn: Sheldon Cooper
objectClass: person
objectClass: inetOrgPerson
sn: Cooper

dn: cn=Leonard Hofstadter,ou=People,dc=homestead,dc=localdomain
cn: Leonard Hofstadter
objectClass: person
objectClass: inetOrgPerson
sn: Hofstadter

dn: cn=Howard Wolowitz,ou=People,dc=homestead,dc=localdomain
cn: Howard Wolowitz
objectClass: person
objectClass: inetOrgPerson
sn: Wolowitz

dn: cn=Rajesh Koothrappali,ou=People,dc=homestead,dc=localdomain
cn: Rajesh Koothrappali
objectClass: person
objectClass: inetOrgPerson
sn: Koothrappali

Load the data:

ldapadd -x -W -D "cn=admin,dc=homestead,dc=localdomain" -f users.ldif

(You'll be prompted for the admin password.)

Verify the records using:

ldapsearch -x -b "dc=homestead,dc=localdomain" -s sub "objectclass=*"

(PHP Interaction, Connecting to the Server, Searching, Updating, and Deleting will follow in subsequent sections, due to length limitations.)

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