Let’s say you have the following 2D associative array in PHP of fruits and their corresponding prices and you want to have them sorted by price:

$fruits = array
(
    [0] => array
        (
            ['product'] => 'banana',
            ['price']     => 2.99
        ),
    [1] => array
        (
            ['product'] => 'apple',
            ['price']     => 1.99
        ),
    [2] => array
        (
            ['product'] => 'durian',  //these smell by the way - i do not know how people can like them =)
            ['price']     => 19.99
        ),
    [3] => array
        (
            ['product'] => 'starfruit', //not too stinky but still stinky nonetheless
            ['price']     => 5.99
        )
);

The answer to this one involves the use of the PHP function, usort, which allows users to define their own comparison function for sorting arrays of all shapes and sizes.

For this example, our function would need to be defined as the following if we wanted to have the prices descending:

function sortDescending ($a, $b)
{
    if ($a['price'] == $b['price']) {
        return 0;
    }
    return ($a['price'] > $b['price']) ? -1 : 1;
}

Here is the slightly different version of the function for an ascending sort:

function sortAscending ($a, $b)
{
    if ($a['price'] == $b['price']) {
        return 0;
    }
    return ($a['price'] < $b['price']) ? -1 : 1;
}

To put it all together in a descending sort, we have the following:

function sortDescending ($a, $b)
{
    if ($a['price'] == $b['price']) {
        return 0;
    }
    return ($a['price'] > $b['price']) ? -1 : 1;
}
usort($fruits, "sortDescending");
 
foreach ($fruits as $fruit) {
    echo $fruit['product'] . ": " . $fruit['price'] . "\n";
}

This would give us the following output:

durian: 19.99
starfruit: 5.99
banana: 2.99
apple: 1.99


1
2
3
4

$res = mysql_query("SELECT date FROM times;");
while ( $row = mysql_fetch_array($res) ) {
   echo $row['date'] . "<br />";
}

This date format that is in the output is in the timestamp format, 2008-10-05 21:34:02, which is not surprising, but you want something that is more “user-friendly” or “readable” as in “9:34 pm October 5, 2008.”

Let’s go back to the drawing board and try again:

1
2
3
4

$res = mysql_query("SELECT date FROM times;");
while ( $row = mysql_fetch_array($res) ) {
   echo date("g:i a F j, Y ", strtotime($row["date"])) . "<br />";
}

A sample output from this PHP code would be 9:34 pm October 5, 2008 which is much more user-friendly.

The PHP strtotime function parses the MySQL timestamp into a Unix timestamp which can be utilized for further parsing or formatting in the PHP date function.

Here are some other sample date output formats that may be of practical use:

1
2
3
4
5
6

echo date("F j, Y g:i a", strtotime($row["date"]));                  // October 5, 2008 9:34 pm
echo date("m.d.y", strtotime($row["date"]));                         // 10.05.08
echo date("j, n, Y", strtotime($row["date"]));                       // 5, 10, 2008
echo date("Ymd", strtotime($row["date"]));                           // 20081005
echo date('\i\t \i\s \t\h\e jS \d\a\y.', strtotime($row["date"]));   // It is the 5th day.
echo date("D M j G:i:s T Y", strtotime($row["date"]));               // Sun Oct 5 21:34:02 PST 2008