dba_handlers

(PHP 4 >= 4.3.0, PHP 5, PHP 7)

dba_handlers — List all the handlers available

说明

array dba_handlers ([ bool $full_info = false ] )

dba_handlers() list all the handlers supported by this extension.

参数

full_info: Turns on/off full information display in the result.

返回值

Returns an array of database handlers. If full_info is set to TRUE, the array will be associative with the handlers names as keys, and their version information as value. Otherwise, the result will be an indexed array of handlers names.

Note:
When the internal cdb library is used you will see cdb and cdb_make.

范例

Example #1 dba_handlers() Example


<?php

echo "Available DBA handlers:\n";
foreach (dba_handlers(true) as $handler_name => $handler_version) {
  // clean the versions
  $handler_version = str_replace('$', '', $handler_version);
  echo " - $handler_name: $handler_version\n";
}

?>

以上例程的输出类似于：

Available DBA handlers:
 - cdb: 0.75, Revision: 1.3.2.3 
 - cdb_make: 0.75, Revision: 1.2.2.4 
 - db2: Sleepycat Software: Berkeley DB 2.7.7: (08/20/99)
 - inifile: 1.0, Revision: 1.6.2.3 
 - flatfile: 1.0, Revision: 1.5.2.4

User Contributed Notes

cbemerine at gmail dot com 06-Sep-2009 02:59


A quick way to see which DBA handlers, without version numbers, that have been built into your version of MySQL on your system, use var_dump with dba_handler() as follows: 



<?php

var_dump ( "dba_handlers()" ); 

?>



Many distros build in these DBA Handlers by default: 

array(5) { [0]=>  string(3) "cdb" [1]=>  string(8) "cdb_make" [2]=>  string(3) "db4" [3]=>  string(7) "inifile" [4]=>  string(8) "flatfile" }



using print and pre tags for readability: 



array(5) {



  [0]=>



  string(3) "cdb"



  [1]=>



  string(8) "cdb_make"



  [2]=>



  string(3) "db4"



  [3]=>



  string(7) "inifile"



  [4]=>



  string(8) "flatfile"



}



Note there are issues with dba_insert and dba_replace without building for either GDBM or QDBM.

  Here are two sources for the list of DBA handlers: (http://www.php-editors.com/php_manual/ref.dba.html and http://dewa03.unep.org/manuals/php_manual/ref.dba.html; )



CDBM & CDB compiles have issues with updates, you can read databases and write new database files, but you will be prevented from using dba_replace() and you may have issues with dba_insert().



NDBM & DBM are depreciated.



DB2, DB3 & DB4 (Berkeley DB Sleepycat Software / Oracle)  Have read online about issues with dba_replace() and db4 specifically. Make sure you test your installation for correct usage of all DBA functions.



SDBM, TDB, TinyCDB were not listed on most of the sources I have found online.  Those DBA handlers and the names of the developers were listed on the QDBM source forge site.  How they interact with dba_replace() I do not know.  You should be aware of their existence.  



GDBM and QDBM are the only other two DBA handlers I am aware of.  Both are reported to allow PHP's dba_replace() function to work correctly so either may be an acceptable option.  The following three restrictions of traditional DBM are not issues for either GDBM or QDBM: 1) a process can handle only one database;  2) the size of a key and a value is bounded;   3) a database file is sparse.



DBA handler benchmark compares QDBM, GDBM, NDBM, SDBM, TDB, CDB, BDB, QDBM-BT-ASC, QDBM-BT-RND, BDB-BT-ASC, BDB-BT-RND can be found here: (http://qdbm.sourceforge.net/benchmark.pdf); 



QDBM seems to offer significant improvements in speed over the other DBA Handlers, test in your environment to verify the results.