# LDAP Functions

## Introduction

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 structure.

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:

         /usr/local/myapp/docs

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 available.

Lots of information about LDAP can be found at

- » Mozilla

- » OpenLDAP Project

The Netscape SDK contains a helpful » Programmer's Guide in HTML format.

## Requirements

You will need to get and compile LDAP client libraries from either » OpenLDAP or » Bind9.net in order to compile PHP with LDAP support.

## Installation

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: Note to Win32 Users In order for this extension to work, there are DLL files that must be available to the Windows system PATH. See the FAQ titled "How do I add my PHP directory to the PATH on Windows" for information on how to do this. Although copying DLL files from the PHP folder into the Windows system directory also works (because the system directory is by default in the systems PATH), it is not recommended. This extension requires the following files to be in the PATH: libeay32.dll and ssleay32.dll
> Versions before PHP 4.3.0 additionally require libsasl.dll.

In order to use Oracle LDAP libraries, proper Oracle environment has to be set.

## Runtime Configuration

The behaviour of these functions is affected by settings in php.ini.

LDAP configuration options
Name | Default | Changeable | Changelog
--- | --- | --- | ---
ldap.max_links | "-1" | PHP_INI_SYSTEM |

For further details and definitions of the PHP_INI_* constants, see the php.ini directives.

## Resource Types

Most LDAP functions operate on or return resources (e.g. ldap_connect() returns a positive LDAP link identifier required by most LDAP functions).

## Predefined Constants

The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.

`LDAP_DEREF_NEVER` (integer)
`LDAP_DEREF_SEARCHING` (integer)
`LDAP_DEREF_FINDING` (integer)
`LDAP_DEREF_ALWAYS` (integer)
`LDAP_OPT_DEREF` (integer)
`LDAP_OPT_SIZELIMIT` (integer)
`LDAP_OPT_TIMELIMIT` (integer)
`LDAP_OPT_NETWORK_TIMEOUT` (integer)
  Option for ldap_set_option() to allow setting network timeout. (Available as of PHP 5.3.0)
`LDAP_OPT_PROTOCOL_VERSION` (integer)
`LDAP_OPT_ERROR_NUMBER` (integer)
`LDAP_OPT_REFERRALS` (integer)
`LDAP_OPT_RESTART` (integer)
`LDAP_OPT_HOST_NAME` (integer)
`LDAP_OPT_ERROR_STRING` (integer)
`LDAP_OPT_MATCHED_DN` (integer)
`LDAP_OPT_SERVER_CONTROLS` (integer)
`LDAP_OPT_CLIENT_CONTROLS` (integer)
`LDAP_OPT_DEBUG_LEVEL` (integer)
`GSLC_SSL_NO_AUTH` (integer)
`GSLC_SSL_ONEWAY_AUTH` (integer)
`GSLC_SSL_TWOWAY_AUTH` (integer)

## Examples

Retrieve information for all entries where the surname starts with "S" from a directory server, displaying an extract with name and email address.

Example#1 LDAP search example

`<?php
// basic sequence with LDAP is connect, bind, search, interpret search
// result, close connection
echo "<h3>LDAP query test</h3>";
echo "Connecting ...";
$ds=ldap_connect("localhost"); // must be a valid LDAP server!
echo "connect result is " . $ds . "<br />";
if ($ds) {
echo "Binding ...";
$r=ldap_bind($ds); // this is an "anonymous" bind, typically
// read-only access
echo "Bind result is " . $r . "<br />";
echo "Searching for (sn=S*) ...";
// Search surname entry
$sr=ldap_search($ds, "o=My Company, c=US", "sn=S*");
echo "Search result is " . $sr . "<br />";
echo "Number of entires returned is " . ldap_count_entries($ds, $sr) . "<br />";
echo "Getting entries ...<p>";
$info = ldap_get_entries($ds, $sr);
echo "Data for " . $info["count"] . " items returned:<p>";
for ($i=0; $i<$info["count"]; $i++) {
echo "dn is: " . $info[$i]["dn"] . "<br />";
echo "first cn entry is: " . $info[$i]["cn"][0] . "<br />";
echo "first email entry is: " . $info[$i]["mail"][0] . "<br /><hr />";
}
echo "Closing connection";
ldap_close($ds);
} else {
echo "<h4>Unable to connect to LDAP server</h4>";
}
?>`

## Using the PHP LDAP calls

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 Company,c=US")

- 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"

## Table of Contents

- ldap_8859_to_t61 — Translate 8859 characters to t61 characters
- ldap_add — Add entries to LDAP directory
- ldap_bind — Bind to LDAP directory
- ldap_close — Alias of ldap_unbind
- ldap_compare — Compare value of attribute found in entry specified with DN
- ldap_connect — Connect to an LDAP server
- ldap_count_entries — Count the number of entries in a search
- ldap_delete — Delete an entry from a directory
- ldap_dn2ufn — Convert DN to User Friendly Naming format
- ldap_err2str — Convert LDAP error number into string error message
- ldap_errno — Return the LDAP error number of the last LDAP command
- ldap_error — Return the LDAP error message of the last LDAP command
- ldap_explode_dn — Splits DN into its component parts
- ldap_first_attribute — Return first attribute
- ldap_first_entry — Return first result id
- ldap_first_reference — Return first reference
- ldap_free_result — Free result memory
- ldap_get_attributes — Get attributes from a search result entry
- ldap_get_dn — Get the DN of a result entry
- ldap_get_entries — Get all result entries
- ldap_get_option — Get the current value for given option
- ldap_get_values_len — Get all binary values from a result entry
- ldap_get_values — Get all values from a result entry
- ldap_list — Single-level search
- ldap_mod_add — Add attribute values to current attributes
- ldap_mod_del — Delete attribute values from current attributes
- ldap_mod_replace — Replace attribute values with new ones
- ldap_modify — Modify an LDAP entry
- ldap_next_attribute — Get the next attribute in result
- ldap_next_entry — Get next result entry
- ldap_next_reference — Get next reference
- ldap_parse_reference — Extract information from reference entry
- ldap_parse_result — Extract information from result
- ldap_read — Read an entry
- ldap_rename — Modify the name of an entry
- ldap_sasl_bind — Bind to LDAP directory using SASL
- ldap_search — Search LDAP tree
- ldap_set_option — Set the value of the given option
- ldap_set_rebind_proc — Set a callback function to do re-binds on referral chasing
- ldap_sort — Sort LDAP result entries
- ldap_start_tls — Start TLS
- ldap_t61_to_8859 — Translate t61 characters to 8859 characters
- ldap_unbind — Unbind from LDAP directory