1st. dbmreplace is not working 
2nd. first character of value disappears sometimes:
This my code:
<?
  echo "<br><b>dblist function</b> ".dblist();   
  //$aArray=array("1st"=>"Dbase" , "2nd"=>"Access" , "3rd"=>"Oracle" , "4th"=>"Sybase");
  $db=dbmopen("dbtest.dbm", "c") or die("Can't create database \n");
  echo "<br>Database Opened";
  // insert/replace array into database
  while (list ($key, $val) = each ($aArray)) {
     echo "<br> $key => $val //-> function returned = \n";
     if ( dbmexists($db, $key) ) {
       echo "Replace => ".dbmreplace($db, $key, $val) ;
     } else { 
       echo "Insert => ".dbminsert($db, $key, $val) ;
     }
  } 
  // listing  dbatabase  
  echo "<P> Listing Database \n";  
  $key = dbmfirstkey($db);
  while ($key) {
     echo "<br>$key = " . dbmfetch($db, $key) . "\n";
     $key = dbmnextkey($db, $key);
  }
  echo "<P> Closing Database \n";  
  dbmclose($db) or die("<br>dbmclose failled</b> \n");  

This code produces :

Database Opened
1st => Dbase //-> function returned = Insert => 0
2nd => Access //-> function returned = Insert => 0
3rd => Oracle //-> function returned = Insert => 0
4th => Sybase //-> function returned = Insert => 0

Listing Database 
1st = base3      
2nd = ccess3 
3rd = Oracle 
4th = ybasee 

Closing Database