XX. DBM

Ces fonctions vous permettent d'�crire des lignes dans une base de donn�es de type dbm. Ce type de base (support� par Berkeley db, gdbm, et quelques librairies syst�mes, ou certaines librairies du syst�me d'exploitation) enregistre les paires cl�s/valeurs, (contrairement aux enregistrements par ligne, utilis� par les autres bases de donn�es relationnelles).

Exemple 1. Pr�sentation de dbm

<?php
  $dbm = dbmopen("dernier", "w");
  if (dbmexists($dbm, $userid)) {
    $last_seen = dbmfetch($dbm, $userid);
  } else {
    dbminsert($dbm, $userid, time());
  }
  faire_quelquechose();
  dbmreplace($dbm, $userid, time());
  dbmclose($dbm);
?>

Table des mati�res
dblist -- D�crit la librairie dbm utilis�e.
dbmclose -- Ferme une base de donn�es dbm.
dbmdelete -- Efface une valeur.
dbmexists -- Indique si une valeur existe.
dbmfetch -- Lit une valeur.
dbmfirstkey -- Lit la premi�re cl�.
dbminsert -- Ins�re une valeur.
dbmnextkey -- Lit la cl� suivante.
dbmopen -- Ouvre une base de donn�es dbm
dbmreplace -- Remplace une valeur.

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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