If your oracle database is on a remote system within your local network and you don't want to worry about the tnsnames file you can try this.

$db = "(DESCRIPTION=(ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.XX.XXX)(PORT = 1521)))(CONNECT_DATA=(SID=XXXX)))";

$c1 = ocilogon("name","password",$db);

Hope this helps someone.

ONE ALTERNATIVE OF CONNECT IN ORACLE RAC "Real Application Clusters"

<?php
$dbstr ="(DESCRIPTION =(ADDRESS = (PROTOCOL = TCP)(HOST =ip1)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = banco)
(INSTANCE_NAME = banco1)))"; 
 
$dbstr1 ="(DESCRIPTION =(ADDRESS = (PROTOCOL = TCP)(HOST =ip2)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = banco)
(INSTANCE_NAME = banco2)))"; 
 
if(!@($conn = oci_connect('user','password',$dbstr1)))
{ $conn = oci_connect('user','password',$dbstr) or die (ocierror()); }
?>

If you want to specify a connection timeout in case there is network problem, you can edit the client side (e.g. PHP side) sqlnet.ora file and set SQLNET.OUTBOUND_CONNECT_TIMEOUT. This sets the upper time limit for establishing a connection right through to the DB, including the time for attempts to connect to other services.   It is available from Oracle 10.2.0.3 onwards.

In Oracle 11.1, a slightly lighter-weight solution TCP.CONNECT_TIMEOUT was introduced.  It also is a sqlnet.ora parameter.  It bounds just the TCP connection establishment time, which is mostly where connection problem are seen.

The client sqlnet.ora file should be put in the same directory as the tnsnames.ora file.

Using ldap for Oracle name resolution:

  The web server will need the environmental variable TNS_ADMIN='Directory of tnsname.ora' unless the default location is used. I use '/etc/tns_admin'. Confirm using the phpinfo().

  There are three files needed in the TNS_ADMIN location: tnsnames.ora, sqlnet.ora and ldap.ora. If you are only using ldap, tnsnames.ora is not needed.

  To sqlnet.ora add:
     NAMES.DIRECTORY_PATH=(TNSNAMES,LDAP)

  To ldap.ora add:
     DIRECTORY_SERVERS=(ldap_server_fqdn:port)
     DEFAULT_ADMIN_CONTEXT=""
     DIRECTORY_SERVER_TYPE=OID

  For a quick and dirty ldap tnsnames server use tnsManager by Dave Berry. Oracle OID or Openldap can used, but are complicated to setup. tnsManager is a no brainer. The quick part: give it a tnsnames.ora file and start it up. The dirty parts: I can't get Toad and SQLDeveloper to work with it, it ignores the domain and it is no longer being maintained.

  The order of values in NAMES.DIRECTORY_PATH in sqlnet.ora determines which look up 'adapter' is used, in this case it is tnsnames.ora file and then ldap. I use ldap for general consumption and tnsnames.ora file to override ldap or entries that are not for general consumption.

  If you have the full Oracle client you have tnsping. 'tnsping ORACLE_SID' will tell you what adapter you are using: 'Used LDAP adapter to resolve the alias'.

<?php
  echo system("/PATH/tnsping ".$ORACLE_SID." 2>&1")."<br />";
  echo 'TNS_ADMIN='.getenv('TNS_ADMIN');
?>

ISSUE:
  If connecting with only ORACLE_SID and not ORACLE_SID.DB_DOMAIN, the value of NAMES.DEFAULT_DOMAIN from sqlnet.ora is appended, then for some reason PHP tries the HOSTNAME adapter, and if the database name resolves in DNS, it will fail connecting using the database name as the hostname, because neither SID nor SERVICE_NAME are defined.
  If using tnsManager append '.ANY_DOMAIN' to $ORACLE_SID to hack around the issue above.

  I have tested with:
       11.1.0.7 full client and PHP 5.1.6
       11.2.0.2 full client and PHP 5.4.11

  I have heard that LDAP lookup does not work with older instantclients.

When you are using Oracle 9.2+ I would say that you MUST use the CHARSET parameter.

Of course, you will not notice it until there is accented character... so just specify it and you will avoid a big headache.

So for example here is our Oracle internal conf:
select * from nls_database_parameters;
 
PARAMETER                      VALUE
------------------------------ ----------------------------------------
…
NLS_LANGUAGE                   AMERICAN
NLS_TERRITORY                  AMERICA
NLS_ISO_CURRENCY               AMERICA
NLS_CHARACTERSET               WE8ISO8859P15
…
 
And there our oci_connect call:

$dbch=ocilogon($user,$pass,$connectString,"WE8ISO8859P15");

Without that, you will get question mark (inversed), squares… instead of most accented character.

Don’t forget to use that for writing as well as for reading.

Regarding the following statement in the documentation:
"The second and subsequent calls to oci_connect() with the same parameters will return the connection handle returned from the first call."

There's one caveat here.  Subsequent calls to oci_connect() will only return the same connection handle as the first call as long as a reference is held to the original handle.

For example, the following code will generate *one* connection handle:

<?php
$dbh = oci_connect($username, $password, $conn_info);
// Do stuff
$dbh = oci_connect$username, $password, $conn_info);
// Do more stuff

The follow code will generate *two* connection handles:
getData();
// Do stuff
getData();
// Do more stuff

getData() {
    $dbh = oci_connect($username, $password, $conn_info);
    // Do stuff
}
?>

This is the result of PHP garbage collecting the handle at the end of the method scope.

If you want to isolate your DB layer through function calls but still want to leverage the fact that oci_connect can return the same handle, just keep a reference to the handle like so:

<?php
getData($username, $password, $conn_info) {
    $dbh = oci_connect($username, $password, $conn_info);
    $key = hash('md5', "$username|$password|$conn_info");
    $GLOBALS[$key] = $dbh;
    // Do stuff
}
?>

I originally logged this as a bug but apparently this is the expected behaviour, likely because oci_close($dbh) just calls unset($dbh).

When using the OCI_CRED_EXT in php 
if the ENV $ORACLE_SID is set the DB does not need to be specified explicitly and the connection will fail unless you provide a NULL DB value when creating the connection. 

The $ORACLE_SID trumps the TNS name look up for the connection. So even a manual connection string in the DB parameter will fail.

So when the $ORACLE_SID Env is set a NULL passed instead of the DB name connects successfully. 

Hope this saves some hair pulling when moving to %.3 and OS Authentications

There is a useful solution to the problem of securing connection information in the PHP Cookbook (O'Reilly) by David Sklar and Adam Trachtenberg. They propose using 'SetEnv' in the Apache configuration and then accessing the values from within a script using $_SERVER.

Unfortunately using the 'SetEnv' solution exposes your connection information to all users of that virtual host. If they run phpinfo.php or display $_SERVER, I found that they will see the password from any file under the root of that virtual host.

To restrict exposure to a particular directory or specific file:

1. First put an 'Include' to the secret file in httpd.conf. For example:

Include "/web/private/secret.txt"

2. In the password file, use the 'SetEnvIf' directive to enable the Environment variables by directory only or within a specific file. For example:

- For all files in the directory:

SetEnvIf Request_URI "/path/to/my/directory" ORACLE_PASS=5gHj790j

- For a specific file in the directory

SetEnvIf Request_URI "/path/to/my/directory/connection.oracle.php" ORACLE_PASS=5gHj790j

Using ldap for Oracle name resolution:

  The web server needs the environmental variable TNS_ADMIN='Directory of tnsname.ora'. I use '/etc/tns_admin'. Confirm using the phpinfo() function.

  There are three files needed in the TNS_ADMIN location: tnsnames.ora, sqlnet.ora and ldap.ora. If you are only using ldap, tnsnames.ora is not needed.

  To sqlnet.ora add: 
     NAMES.DIRECTORY_PATH=(TNSNAMES,LDAP)

  To ldap.ora add:
     DIRECTORY_SERVERS=(ldap_fqdn_hostname:1575)
     DEFAULT_ADMIN_CONTEXT=""
     DIRECTORY_SERVER_TYPE=OID

  For a quick and dirty ldap tnsnames server use tnsManager by Dave Berry. Oracle OID or Openldap can used, but are complicated to setup. tnsManager is a no brainer. The default port is 1575.

  The order of values in NAMES.DIRECTORY_PATH from sqlnet.ora determines which look up 'adapter' is used first, in this case it is tnsnames.ora file and then ldap. I use ldap for general consumption and tnsnames.ora file to override ldap or entries that are not for general consumption.

  If you have the full Oracle client you have tnsping. 'tnsping ORACLE_SID' will tell you what adapter you are using: 'Used LDAP adapter to resolve the alias'.

<?php
  echo system("/PATH/tnsping ".$ORACLE_SID." 2>&1")."<br />";
  echo 'TNS_ADMIN='.getenv('TNS_ADMIN');
?>

ISSUE:
  For some reason PHP tries the HOSTNAME adapter first, and if the database name resolves in DNS, it will try connecting using the database name as the hostname with no SID or SERVICE_NAME defined. All other Oracle clients I have used will not try the HOSTNAME adapter unless it is listed in NAMES.DIRECTORY_PATH.
  I have heard that LDAP look up does not work with older instantclients.