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
The Netscape SDK contains a helpful » Programmer's Guide in HTML format.
You will need to get and compile LDAP client libraries from either » OpenLDAP or » Bind9.net in order to compile PHP with LDAP support.
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.
这些函数的行为受 php.ini 的影响。
| Name | Default | Changeable | Changelog |
|---|---|---|---|
| ldap.max_links | "-1" | PHP_INI_SYSTEM |
Most LDAP functions operate on or return resources (e.g. ldap_connect() returns a positive LDAP link identifier required by most LDAP functions).
以下常量由本扩展模块定义，因此只有在本扩展模块被编译到 PHP 中，或者在运行时被动态加载后才有效。
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>";
}
?>
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"