PHP 连接 DNS

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DSN and DSN-less connections[/td]<!---->[td=1,1,100%]

　　DSN stands for 'Data Source Name'. It is an easy way to assignuseful and easily rememberable names to data sources which may not belimited to databases alone. If you do not know how to set up a systemDSN read our tutorial How to set up a system DSN.
　　For our example below lets assume that our DSN points to an Accessdatabase called 'examples.mdb' and that we will be selecting recordsfrom the table 'cars'.

<?php //connect to a DSN "myDSN" $conn = odbc_connect('myDSN','',''); if ($conn) {   //the SQL statement that will query the database   $query = "select * from cars";   //perform the query   $result=odbc_exec($conn, $query);   echo "<table border=\"1\"><tr>";   //print field name   $colName = odbc_num_fields($result);   for ($j=1; $j<= $colName; $j++)   {      echo "<th>";     echo odbc_field_name ($result, $j );     echo "</th>";   }   //fetch tha data from the database   while(odbc_fetch_row($result))   {     echo "<tr>";     for($i=1;$i<=odbc_num_fields($result);$i++)      {       echo "<td>";       echo odbc_result($result,$i);       echo "</td>";     }     echo "</tr>";   }   echo "</td> </tr>";   echo "</table >";   //close the connection   odbc_close ($conn); } else echo "odbc not connected"; ?>

　　Remember that 'myDSN' above is name of the DSN. Also note that youcan change the table name from 'cars' to the name of your table andpoint the DSN to whatever database you like. One other thing toremember is that you can set up a DSN on your own machine though if youare using a hosting company you may have to ask the webmaster.
DSN-less connection
　　DSN-less connections don't require creation of system level DSNs forconnecting to databases and provide an alternative to DSNs. We will nowsee how to connect to a database via PHP using Connection String inplace of DSN name.
<?php

//create an instance of the  ADO connection object
$conn = new COM ("ADODB.Connection")
  or die("Cannot start ADO");

//define connection string, specify database driver
$connStr = "PROVIDER=Microsoft.Jet.OLEDB.4.0;Data Source= c:\inetpub\wwwroot\db\examples.mdb";
  $conn->open($connStr); //Open the connection to the database

//declare the SQL statement that will query the database
$query = "SELECT * FROM cars";

//execute the SQL statement and return records
$rs = $conn->execute($query);

$num_columns = $rs->Fields->Count();
echo $num_columns . "<br>"; 

for ($i=0; $i < $num_columns; $i++) {
    $fld[$i] = $rs->Fields($i);
}

echo "<table>"; while (!$rs->EOF)  //carry on looping through while there are records
{
    echo "<tr>";
    for ($i=0; $i < $num_columns; $i++) {
        echo "<td>" . $fld[$i]->value . "</td>";
    }
    echo "</tr>";
    $rs->MoveNext(); //move on to the next record
}


echo "</table>";

//close the connection and recordset objects freeing up resources 
$rs->Close();
$conn->Close();

$rs = null;
$conn = null;
?>