[string|null$connection_string = null],
[string$encoding = ""],
[int$session_mode = OCI_DEFAULT]
Creates a persistent connection to an Oracle server and logs on.
Persistent connections are cached and re-used between requests, resulting in reduced overhead on each page load; a typical PHP application will have a single persistent connection open against an Oracle server per Apache child process (or PHP FPM process). See the OCI8 Connection Handling and Connection Pooling section for more information.
The Oracle user name.
The password for username.
the Oracle instance to connect to. It can be
an Easy Connect
string, or a Connect Name from
the tnsnames.ora file, or the name of a local
If not specified or null, PHP uses environment variables such as TWO_TASK (on Linux) or LOCAL (on Windows) and ORACLE_SID to determine the Oracle instance to connect to.
To use the Easy Connect naming method, PHP must be linked with Oracle 10g or greater Client libraries. The Easy Connect string for Oracle 10g is of the form: [//]host_name[:port][/service_name]. From Oracle 11g, the syntax is: [//]host_name[:port][/service_name][:server_type][/instance_name]. Further options were introduced with Oracle 19c, including timeout and keep-alive settings. Refer to Oracle documentation. Service names can be found by running the Oracle utility lsnrctl status on the database server machine.
The tnsnames.ora file can be in the Oracle Net search path, which includes /your/path/to/instantclient/network/admin, $ORACLE_HOME/network/admin and /etc. Alternatively set TNS_ADMIN so that $TNS_ADMIN/tnsnames.ora is read. Make sure the web daemon has read access to the file.
Determines the character set used by the Oracle Client libraries. The character set does not need to match the character set used by the database. If it doesn't match, Oracle will do its best to convert data to and from the database character set. Depending on the character sets this may not give usable results. Conversion also adds some time overhead.
If not specified, the Oracle Client libraries determine a character set from the NLS_LANG environment variable.
Passing this parameter can reduce the time taken to connect.
This parameter is available since version PHP 5 (PECL OCI8 1.1) and accepts the following values: OCI_DEFAULT, OCI_SYSOPER and OCI_SYSDBA. If either OCI_SYSOPER or OCI_SYSDBA were specified, this function will try to establish privileged connection using external credentials. Privileged connections are disabled by default. To enable them you need to set oci8.privileged_connect to On.
PHP 5.3 (PECL OCI8 1.3.4) introduced the OCI_CRED_EXT mode value. This tells Oracle to use External or OS authentication, which must be configured in the database. The OCI_CRED_EXT flag can only be used with username of "/" and a empty password. oci8.privileged_connect may be On or Off.
OCI_CRED_EXT may be combined with the OCI_SYSOPER or OCI_SYSDBA modes.
OCI_CRED_EXT is not supported on Windows for security reasons.
Returns a connection identifier or false on error.
Starting with PHP 5.1.2 and PECL OCI8 1.1, the lifetime and maximum number of persistent Oracle connections per PHP process can be tuned by setting the following configuration values: oci8.persistent_timeout, oci8.ping_interval and oci8.max_persistent.