PHP sorting by field?

Question

I have the following array which I populated from MySQL:

print_r ($table);

[0] => Array (
[0] => 67122
[idweather] => 67122
[1] => 2014-09-19 00:04:54   
[date] => 2014-09-19 00:04:54
[2] => 1
[rainfall] => 1
[3] => 10
[windspeed] => 10
[4] => 13.85
[dewpoint] => 13.85  
[5] => 1009.43
[pressure] => 1009.43
[6] => 22.8
[bmp085_temp] => 22.8
[7] => 22.8
[dht22_temp] => 22.8
[8] => 11.58
[abs_hum] => 11.58  
[9] => 45.12
[gust] => 45.12
[10] => 0.18
[uvi] => 0.18
[11] => 97.42
[light] => 97.42
[12] => 57.1
[rel_humidity] => 57.1
[13] =>
[wind_dir] =>
)

This is just [0] - the array contains multiple entries for the day. I would like run multiple sorts so I can get the max rainfall, windspeed, bmp085_temp etc for the day

How do I use the sort like this:

sort($table['wind_dir'];

Not sure if this syntax is right as I get:

PHP Warning:  sort() expects parameter 1 to be array, null given in test.php on line 167

If it helps this is the mysql code:

$sql_array = "select * from weather where date(date) = curdate();";

if(!$result = $db->query($sql_array)){
    die('error running query'); 
}

$table = array();

while ($row = $result->fetch_array()) {
    $table[] = $row;
}

Update:

Ive tried this example:

usort($table, function($a, $b) {
return $a['dht22_temp'] - $b['dht22_temp'];
});

While it appears to be sorting something its not sorted correctly.

echo $table[0]['dht22_temp'];

Prints out a value but its neither the highest or the lowest :(

Update 2:

Got it working with this:

function compare($a, $b)
 {
  return strnatcmp($a['pressure'], $b['pressure']);
 }
usort($table, 'compare');

Check out the function array_multisort, it can do these things: nl3.php.net/manual/en/function.array-multisort.php — Erik
– Erik, Commented Sep 19, 2014 at 8:15

Kevin · Accepted Answer · 2014-09-19 08:18:33Z

1

I suggest use fetch_assoc() in this case. So that in here:

$data = array();
while($row = $result->fetch_assoc()) {
    $data['windspeed'][] = $row['windspeed'];
    $data['rainfall'][] = $row['rainfall'];
}

rsort($data['rainfall']); // reverse descending
$max_rainfall = reset($data['rainfall']); // get the first

Or:

$max_rainfall = max($data['rainfall']);

answered Sep 19, 2014 at 8:18

Kevin

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8 Comments

Greg Over a year ago

Thanks all - the fetch_assoc makes things a lot clearer. Will look into multisort as I need to get the max temp and date associated with it as well.

Kevin Over a year ago

@Greg yes, you really don't need those numeric indices anyway, just the ones with associative keys

Kevin Over a year ago

@Greg by they way, how many rows does this query yield anyway?

Greg Over a year ago

288 rows - values are collected every 5 mins and Im only looking at the max/min for the day.

Kevin Over a year ago

@Greg if thats the case you could try my answer, gather all rainfall inside a container in an array, then just use max() on that container, should give you the highest value

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