Using json_encode() to pass into JavaScript from PHP PDO causes a duplicate in the foreach in this code

Question

<?php
try {
   $conn = new PDO('mysql:host='.$host.';dbname='.$dbname, $username, $password);
   $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
   $data = $conn->query('SELECT id FROM products');
   foreach($data as $row) {
     $r[] = json_encode($row);
   }
} catch(PDOException $e) { echo 'ERROR: ' . $e->getMessage();} 
?>

<script type="text/javascript">
var jArray = <?php echo json_encode($r); ?>;
function showme(j) {
    for(var i=0; i < j.length; i++){ document.write(j[i]); }
};
showme(jArray);
</script>

results...

{"id":"172","0":"172"}{"id":"173","0":"173"}{"id":"174","0":"174"}...

notice the extra ,"0":"172"

I believe I am getting the error in how I am passing data in the PHP foreach or use of PDO. Honestly I just want the smallest footprint to grab data from MySQL so I can play with JavaScript and the data. Any ideas on getting rid of the extra data (and/or performance improvements on use of PDO)? Please no libraries as I have to (want to) use pure JavaScript and limit the server resources.

Jon · Accepted Answer · 2013-08-19 00:38:05Z

3

You are getting the results in both numerically indexed and associative format because that's the default PDO fetch mode. This can be changed with PDOStatement::setFetchMode.

For example, setting the fetch mode to PDO::FETCH_ASSOC will remove the 0 keys from your result arrays and leave just id:

$data->setFetchMode(PDO::FETCH_ASSOC);
foreach($data as $row) {
    $r[] = json_encode($row);
}

answered Aug 19, 2013 at 0:38

Jon

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