PDO row count - num_rows equivalent - php

Question

I'm moving PHP code from mysql to ms sql server.
This will execute my query:
$r = $db_conn->prepare($sql);
$r->execute();
Before I start processing, I need to count how many rows were returned.
old code:
$r->num_rows;
new code:
$rows = $r->fetchAll(PDO::FETCH_ASSOC);
$rcount = count($rows);
All good, but when I try to access values from 1st row I'm getting nothing...
try {
$row = $r->fetch(PDO::FETCH_ASSOC);
} catch (Exception $ex) {
return 0;
}
I need to repoint to 1st row in my recordset after doing the count, how can I do this without having to requery the database again?
I'm new to PHP, sorry for dumb and probably obvious question.
Thanks in advance.

Answer 1

There isn't a way in PDO to reset the pointer. You could execute the query again, but given that you've already fetched all the data with your call to fetchAll, that is wasteful. Instead, to access the data, simply loop over the $rows array e.g.
foreach ($rows as $row) {
// do something
}
Note that if you expect an exception on fetch, it is likely you might get one on fetchAll too, so you should wrap the call to fetchAll in a try/catch block:
try {
$rows = $r->fetchAll(PDO::FETCH_ASSOC);
} catch (Exception $ex) {
return 0;
}

Answer 2

One possible approach, if you use PHP Driver for SQL Server, is to use PDOStatement::rowCount and client-side cursor. With this type of cursor row count is available after a query is executed, but this type of cursor should be used for small (medium) result sets.
<?php
# Connection
$server = 'server\instance,port';
$database = 'master';
$uid = 'uid';
$pwd = 'pwd';
# PDO Connection
try {
# SQL authentication
$conn = new PDO("sqlsrv:server=$server;Database=$database", $uid, $pwd);
# Windows authentication
#$conn = new PDO("sqlsrv:server=$server;Database=$database");
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch( PDOException $e ) {
die( "Error connecting to SQL Server".$e->getMessage());
}
# Client-side cursor
try {
$options = array(
PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL,
PDO::SQLSRV_ATTR_CURSOR_SCROLL_TYPE => PDO::SQLSRV_CURSOR_BUFFERED
);
$stmt = $conn->prepare("SELECT * FROM master.sys.server_principals", $options);
$stmt->execute();
echo 'Row count: '.$stmt->rowCount().'<br>';
while ($row = $stmt->fetch(PDO::FETCH_ASSOC) ){
echo 'Login name: '.$row['name'].'<br>';
}
} catch( PDOException $e ) {
die( "Error executing query".$e->getMessage() );
}
# End
$stmt = null;
$conn = null;
?>