XX. DBM Functions

Introductie

These functions allow you to store records stored in a dbm-style database. This type of database (supported by the Berkeley DB, , and some system libraries, as well as a built-in flatfile library) stores key/value pairs (as opposed to the full-blown records supported by relational databases).

Opmerking: However, dbm support is deprecated and you are encourged to use the Database (dbm-style) abstraction layer functions instead.

Afhankelijkheden

To use this functions you have to compile PHP with support for an underlying database. See the list of supported Databases.

Installatie

In order to use these functions, you must compile PHP with dbm support by using the --with-db option. In addtion you must ensure support for an underlying database or you can use some sytem libraries.

Configuratie tijdens scriptuitvoer

Deze extensie gebruikt geen configuratie regels.

Resource types

The function dbmopen() returns an database identifier which is used by the other dbm-functions.

Voorgedefineerde constanten

Deze extensie defineert geen constanten.

Voorbeelden

Voorbeeld 1. DBM example

$dbm = dbmopen ("lastseen", "w");
if (dbmexists ($dbm, $userid)) {
    $last_seen = dbmfetch ($dbm, $userid);
} else {
    dbminsert ($dbm, $userid, time());
}
do_stuff();
dbmreplace ($dbm, $userid, time());
dbmclose ($dbm);

Inhoudsopgave
dblist -- Describes the DBM-compatible library being used
dbmclose -- Closes a dbm database
dbmdelete -- Deletes the value for a key from a DBM database
dbmexists -- Tells if a value exists for a key in a DBM database
dbmfetch -- Fetches a value for a key from a DBM database
dbmfirstkey -- Retrieves the first key from a DBM database
dbminsert -- Inserts a value for a key in a DBM database
dbmnextkey -- Retrieves the next key from a DBM database
dbmopen -- Opens a DBM database
dbmreplace -- Replaces the value for a key in a DBM database

Be advised that almost every function in this section either has no documentation or incorrectly documented regarding return codes. If you want to use the DB methods safely you will have to reverse engineer the return codes and hope that they do not change values returned by the functions in the future to match the incorrect documentation. In my experience, the return code of 0 or FALSE indicates no error. This matches the behavior of GDBM which I am using as my underlying DB manager. This may not be true for people using another manager, or the builtin flatfile code.

First: Make a firstdbm.db file. Set attribute Read and Write. -------------------------------------- <html><body> <? $dbm = dbmopen("firstdbm","w"); echo "\$dbm: $dbm = dbmopen(\"firstdbm\", \"w\"); "; echo "".dblist()." = dblist(); "; $fruit = "apple"; $colour = "red"; if (dbmexists ($dbm, $fruit)) { $colour = dbmfetch ($dbm, $fruit); echo "\$colour: $colour = dbmfetch(\$dbm: $dbm, \$fruit: $fruit); "; $key = dbmreplace($dbm, $fruit, "green"); echo "\$key: $key = dbmreplace(\$dbm: $dbm, \$fruit: $fruit, \"green\"); "; $colour = dbmfetch ($dbm, $fruit); echo "\$colour: $colour = dbmfetch(\$dbm: $dbm, \$fruit: $fruit); "; if ( !dbmdelete($dbm, $fruit) ) { echo "False (OK) = dbmdelete(\$dbm: $dbm, \$fruit: $fruit); "; } else { echo "True (NOT OK) = dbmdelete(\$dbm: $dbm, \$fruit: $fruit); "; } $colour = dbmfetch ($dbm, $fruit); echo "\$color: $colour = dbmfetch(\$dbm: $dbm, \$fruit: $fruit); <hr>"; $i = 1; $key = dbmfirstkey($dbm); while ($key) { if ($i==1) { echo "\$key: $key = dbmfirstkey(\$dbm: $dbm); "; } else { echo "\$key: $key = dbmnextkey(\$dbm: $dbm); "; } $i++; $colour = dbmfetch ($dbm, $key); echo "\$colour: $colour = dbmfetch(\$dbm: $dbm, \$key: $key); "; $key = dbmnextkey($dbm,$key); } } else { dbminsert ($dbm, $fruit, $colour); echo "dbminsert(\$dbm: $dbm, \$fruit: $fruit, \$colour: $colour); "; dbminsert ($dbm, "pear", "yellow"); echo "dbminsert(\$dbm: $dbm, \"pear\", \"yellow\"); "; dbminsert ($dbm, "apricot", "pink"); echo "dbminsert(\$dbm: $dbm, \"apricot\", \"pink\"); <hr>"; $i = 1; $key = dbmfirstkey($dbm); while ($key) { if ($i==1) { echo "\$key: $key = dbmfirstkey(\$dbm: $dbm); "; } else { echo "\$key: $key = dbmnextkey(\$dbm: $dbm); "; } $i++; $colour = dbmfetch ($dbm, $key); echo "\$colour: $colour = dbmfetch(\$dbm: $dbm, \$key: $key); "; $key = dbmnextkey($dbm,$key); } } echo " "; if (dbmclose ($dbm)) { echo "True (OK) = dbmclose(\$dbm: $dbm); "; } else { echo "False (NOT OK) = dbmclose(\$dbm: $dbm); "; }; ?> </body></html> -------------------------------------- The first run output: $dbm: 1 = dbmopen("firstdbm", "w"); ndbm support enabled = dblist(); dbminsert($dbm: 1, $fruit: apple, $colour: red); dbminsert($dbm: 1, "pear", "yellow"); dbminsert($dbm: 1, "apricot", "pink"); $key: pear = dbmfirstkey($dbm: 1); $colour: yellow = dbmfetch($dbm: 1, $key: pear); $key: apricot = dbmnextkey($dbm: 1); $colour: pink = dbmfetch($dbm: 1, $key: apricot); $key: apple = dbmnextkey($dbm: 1); $colour: red = dbmfetch($dbm: 1, $key: apple); True (OK) = dbmclose($dbm: 1); -------------------------------------- The second run output: $dbm: 1 = dbmopen("firstdbm", "w"); ndbm support enabled = dblist(); $colour: red = dbmfetch($dbm: 1, $fruit: apple); $key: 0 = dbmreplace($dbm: 1, $fruit: apple, "green"); $colour: green = dbmfetch($dbm: 1, $fruit: apple); False (OK) = dbmdelete($dbm: 1, $fruit: apple); $color: = dbmfetch($dbm: 1, $fruit: apple); $key: pear = dbmfirstkey($dbm: 1); $colour: yellow = dbmfetch($dbm: 1, $key: pear); $key: apricot = dbmnextkey($dbm: 1); $colour: pink = dbmfetch($dbm: 1, $key: apricot); True (OK) = dbmclose($dbm: 1);


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