LDAP is the Lightweight Directory Access Protocol, and is a
protocol used to access "Directory Servers". The Directory is a
special kind of database that holds information in a tree
The concept is similar to your hard disk directory structure,
except that in this context, the root directory is "The world"
and the first level subdirectories are "countries". Lower levels
of the directory structure contain entries for companies,
organisations or places, while yet lower still we find directory
entries for people, and perhaps equipment or documents.
To refer to a file in a subdirectory on your hard disk, you might
use something like:
The forwards slash marks each division in the reference, and the
sequence is read from left to right.
The equivalent to the fully qualified file reference in LDAP is
the "distinguished name", referred to simply as "dn". An example
dn might be:
cn=John Smith,ou=Accounts,o=My Company,c=US
The comma marks each division in the reference, and the sequence
is read from right to left. You would read this dn as:
country = US
organization = My Company
organizationalUnit = Accounts
commonName = John Smith
In the same way as there are no hard rules about how you organise
the directory structure of a hard disk, a directory server
manager can set up any structure that is meaningful for the
purpose. However, there are some conventions that are used. The
message is that you can not write code to access a directory
server unless you know something about its structure, any more
than you can use a database without some knowledge of what is
Lots of information about LDAP can be found at
The Netscape SDK contains a helpful
Programmer's Guide in
LDAP support in PHP is not enabled by default. You will need to
use the --with-ldap[=DIR]
configuration option when compiling PHP to enable LDAP support.
DIR is the LDAP base install directory. To enable SASL support,
be sure --with-ldap-sasl[=DIR] is
used, and that sasl.h exists on the system.
Note to Win32 Users:
In order to enable this module on a Windows environment, you must copy
several files from the DLL folder of the PHP/Win32 binary package to the
SYSTEM folder of your windows machine. (Ex: C:\WINNT\SYSTEM32,
or C:\WINDOWS\SYSTEM). For PHP <= 4.2.0 copy
libsasl.dll, for PHP >= 4.3.0 copy
libeay32.dll and ssleay32.dll to
your SYSTEM folder.
Before you can use the LDAP calls you will need to know ..
The name or address of the directory server you will use
The "base dn" of the server (the part of the world directory
that is held on this server, which could be "o=My
Whether you need a password to access the server (many servers
will provide read access for an "anonymous bind" but require a
password for anything else)
The typical sequence of LDAP calls you will make in an
application will follow this pattern:
ldap_connect() // establish connection to server
ldap_bind() // anonymous or authenticated "login"
do something like search or update the directory
and display the results
ldap_close() // "logout"