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 LXXII. Unified ODBC Functions介绍
     In addition to normal ODBC support, the Unified ODBC functions in
     PHP allow you to access several databases that have borrowed the
     semantics of the ODBC API to implement their own API.  Instead of
     maintaining multiple database drivers that were all nearly
     identical, these drivers have been unified into a single set of
     ODBC functions.
     
     The following databases are supported by the Unified ODBC
     functions: Adabas D,
     IBM DB2,
     iODBC,
     Solid, and
     Sybase SQL Anywhere.
     注: 
      There is no ODBC involved when connecting to the above
      databases. The functions that you use to speak natively to them
      just happen to share the same names and syntax as the ODBC
      functions.  The exception to this is iODBC.  Building PHP with iODBC
      support enables you to use any ODBC-compliant drivers with your PHP
      applications.  iODBC is maintained by 
      OpenLink Software.  More information on iODBC, as well as a
      HOWTO, is available at www.iodbc.org.
     
需求
     To access any of the supported databases you need to have
     the required libraries installed.
    安装
   --with-adabas[=DIR]
      Include Adabas D support. DIR is the Adabas base install directory, 
      defaults to /usr/local.
     --with-sapdb[=DIR]
      Include SAP DB support. DIR is SAP DB base install directory, 
      defaults to /usr/local.
     --with-solid[=DIR]
      Include Solid support. DIR is the Solid base install directory, 
      defaults to /usr/local/solid.
     --with-ibm-db2[=DIR]
      Include IBM DB2 support. DIR is the DB2 base install directory, 
      defaults to /home/db2inst1/sqllib.
     --with-empress[=DIR]
      Include Empress support. DIR is the Empress base install directory, 
      defaults to $EMPRESSPATH. From PHP 4, this option only supports 
      Empress Version 8.60 and above.
     --with-empress-bcs[=DIR]
      Include Empress Local Access support. DIR is the Empress base 
      install directory, defaults to $EMPRESSPATH.  From PHP 4, 
      this option only supports Empress Version 8.60 and above.
     --with-birdstep[=DIR]
      Include Birdstep support. DIR is the Birdstep base install directory, 
      defaults to /usr/local/birdstep.
     --with-custom-odbc[=DIR]
      Include a user defined ODBC support. The DIR is ODBC install base directory, 
      which defaults to /usr/local. Make sure to define
      CUSTOM_ODBC_LIBS and have some odbc.h in your include
      dirs. E.g., you should define following for Sybase SQL Anywhere 5.5.00 on
      QNX, prior to run configure script:
   CPPFLAGS="-DODBC_QNX -DSQLANY_BUG"
   LDFLAGS=-lunix
   CUSTOM_ODBC_LIBS="-ldblib -lodbc".
 
     --with-iodbc[=DIR]
      Include iODBC support. DIR is the iODBC base install directory, 
      defaults to /usr/local.
     --with-esoob[=DIR]
      Include Easysoft OOB support. DIR is the OOB base install directory, 
      defaults to /usr/local/easysoft/oob/client.
     --with-unixODBC[=DIR]
      Include unixODBC support. DIR is the unixODBC base install directory, 
      defaults to /usr/local.
     --with-openlink[=DIR]
      Include OpenLink ODBC support. DIR is the OpenLink base install directory, 
      defaults to /usr/local. This is the same as iODBC.
     --with-dbmaker[=DIR]
      Include DBMaker support. DIR is the DBMaker base install directory, 
      defaults to where the latest version of DBMaker is installed 
      (such as /home/dbmaker/3.6).
     
  To disable unified ODBC support in PHP 3 add
  --disable-unified-odbc to your configure
  line. Only applicable if iODBC, Adabas, Solid, Velocis or a custom ODBC
  interface is enabled.
   PHP 的 Windows 版本已经内置该扩展模块的支持。您无需加载任何附加的扩展库即可使用这些函数。运行时配置这些函数的行为受到全局配置文件 php.ini 的影响。 
   表格 1. Unified ODBC Configuration Options | Name | Default | Changeable | 
|---|
 | odbc.default_db * | NULL | PHP_INI_ALL |  | odbc.default_user * | NULL | PHP_INI_ALL |  | odbc.default_pw * | NULL | PHP_INI_ALL |  | odbc.allow_persistent | "1" | PHP_INI_SYSTEM |  | odbc.check_persistent | "1" | PHP_INI_SYSTEM |  | odbc.max_persistent | "-1" | PHP_INI_SYSTEM |  | odbc.max_links | "-1" | PHP_INI_SYSTEM |  | odbc.defaultlrl | "4096" | PHP_INI_ALL |  | odbc.defaultbinmode | "1" | PHP_INI_ALL | 
注: 
    Entries marked with * are not implemented yet.
   
  For further details and definition of the PHP_INI_* constants see
  ini_set() .
  以下是该配置选项的简要解释。 
  odbc.default_db
    string
     ODBC data source to use if none is specified in
     odbc_connect() or
     odbc_pconnect().
    odbc.default_user
    string
     User name to use if none is specified in
     odbc_connect() or
     odbc_pconnect().
    odbc.default_pw
    string
     Password to use if none is specified in
     odbc_connect() or
     odbc_pconnect().
    odbc.allow_persistent
    boolean
     Whether to allow persistent ODBC connections.
    odbc.check_persistent
    boolean
     Check that a connection is still valid before reuse.
    odbc.max_persistent
    integer
     The maximum number of persistent ODBC connections per process.
    odbc.max_links
    integer
     The maximum number of ODBC connections per process, including
     persistent connections.
    odbc.defaultlrl
    integer
     Handling of LONG fields. Specifies the number of bytes returned to
     variables.
    odbc.defaultbinmode
    integer
     Handling of binary data.
    
预定义常量
由于这些常量是由该扩展模块定义的,因此只有在该扩展模块被编译到 PHP 中,或者在运行时被动态加载后,这些常量才有效。
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