Question

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How to go through mysql result twice?

I have a PHP script with a loop within a loop. The outer loop walks down an array for each $unit in the $unitsarray and query’s a MySQL db to see if there is an entry with the same matching string. If $result1 does indeed return an entry(s), I create another array called $devicetokens array for the row “devicetoken” and then enter my second loop. For each device token, I create an Apple Push Notification to send to an iOS device. I have two problems, first the mysql_query returns nothing. If I replace $unit with a value I know will return na entry, then it works. Second, if I have replace the $unit and get a result back, the $devicetokens array wont populate with any data even though I have a result back from the mysql query. Here is my code:

foreach ($unitsarray as $unit) {

    echo "Unit = $unit </br>";

    // Create array of devices that match the unit
    $result1 = mysql_query("SELECT * FROM `department devices` WHERE unit LIKE '%$unit%'") or die(mysql_error());

    //Print results
    while ($row = mysql_fetch_assoc($result1)) {
        echo "&nbsp;&nbsp;&nbsp;&nbsp;";
        echo $row["device_id"];
        echo " , ";
        echo $row["devicetoken"];
        echo " , ";
        echo $row["unit"];
    }
    echo "</br>";

    $devicetokenarray = array();
    while ($row = mysql_fetch_assoc($result1)) {
        array_push($devicetokenarray, $row["devicetoken"]);
    }

    // Print array
    print_r($devicetokenarray);
    echo "</br>";

    // Loop APNS for each device token in $devicetoken array
    foreach ($devicetokenarray as $devicetoken)
    {

    // Build the binary notification
    $msg = chr(0).pack('n', 32).pack('H*', $devicetoken).pack('n', strlen($payload)).$payload;

    // Send it to the server
    $result = fwrite($fp, $msg, strlen($msg));

    // Create APNS operation output
        if (!$result)
            echo 'Failed message'.PHP_EOL;
        else
            echo "<b>Successful message sent:</b>&nbsp;&nbsp; $call - $location - $station - $units to device(s):&nbsp;&nbsp;'$devicetoken </br>".PHP_EOL;
    }
}

Here’s what my db looks like:

device_id   devicetoken                                         unit

T05 ipad   773f5436825a7115417d3d1e036da20e806efeef547b7c3fe4   121
E05 ipad   773f5436825a7115417d3d1e036da20e806efeef547b7c3fe4   121

Any help would be greatly appreciated!

Answer 1

You are doing a query and storing a result resource in $result1, then fetching all the rows in a loop that you echo out, then immediately trying to fetch it again. Once you fetch all the results, you can’t fetch them again. Well you can, using mysql_data_seek, but it’s really inefficient and wasteful to do so in most cases. Store the results the first time in an array.

$rows = array();

while ($row = mysql_fetch_assoc($result1)) {
     $rows[] = $row;
}

Then you can foreach through this array.

foreach ($rows as $row) {
    // Build the binary notification
    $msg = chr(0).pack('n', 32).pack('H*', $row['devicetoken']) . pack('n', strlen($payload)) . $payload;
    //... etc

}