Sort and display array values according to a value?

Question

Given the following PHP array:

Array
(
    [0] => Array
        (
            [name] => Restaurant 123
            [city] => Arlington
            [zip] => 22201
        )

    [1] => Array
        (
            [name] => Bar Foo
            [city] => Ballston
            [zip] => 22201
         )
     [2] => Array
        (
            [name] => Restaurant XYZ
            [city] => Ballston
            [zip] => 22201
         )

    [3] => Array
        (
            [name] => Restaurant 321
            [city] => Washington DC
            [zip] => 22201
         )

)

How can I produce a list sorted according to city (alphabetically), so that it would output something like:

Arlington

Restaurant 123

Ballston

Bar Foo

Restaurant XYZ

Washington DC

Restaurant 321

EG, sorted first by city name alphabetically, and then by venue name, also alphabetically. Also note that it's not given that the restaurant name, nor the cities are alphabetically sorted in the array given.

Answer 1

Write a callback function that you can pass to usort , for example

function compare_venues($a, $b)
{
  return strcmp($a['name'], $b['name']);
}

Answer 2

您可以使用usort ，它允许您根据用户定义的比较函数对数组进行排序。

Answer 3

Try usort ( http://php.net/manual/en/function.usort.php ) where you can define a custom sort schema like

function cmp($a, $b)
{
    if ($a == $b) {
        return 0;
    }
    return ($a < $b) ? -1 : 1;
}

Answer 4

Looks like theres two parts to what you want - sorting and displaying.

To sort, you want to use usort with small function defining the comparison

$sortFunc = function($a,$b) {return $a['city'] != $b['city'] 
                                 ? $a['city'] > $b['city']
                                 : $a['name'] > $b['name'];};

        // = function($a,$b) {return $a['city'] > $b['city'] || ($a['city'] == $b['city'] && $a['name'] > $b['name']);};
        // = function($a,$b) {return 100*strcmp($a['city'],$b['city']) + strcmp($a['name'],$b['name']);};
usort($arr, $sortFunc);

function displayNamesGroupedByCity($arr)
{
    $lastCity = '';
    foreach($arr as $v)
    {
        if ($v['city'] != $lastCity)
        {
             $lastCity = $v['city'];
             echo "<br /><strong>$lastCity</strong><br />";
        }
        else echo ', ';
        echo $v['name'];
    }
}

displayNamesGroupedByCity($arr);

For the hell of it im going to make things generic

function displayXgroupedByY($arr, $x, $y)
{
    $sortFunc = function($a,$b) use($x,$y) 
                               {return $a[$y] != $b[$y] 
                                 ? $a[$y] > $b[$y]
                                 : $a[$x] > $b[$y];};

    user($arr, $sortFunc);

    $lastCity = '';
    foreach($arr as $v)
    {
        if ($v['city'] != $lastCity)
        {
             $lastCity = $v['city'];
             echo "<br /><strong>$lastCity</strong><br />";
        }
        else echo ', ';
        echo $v['name'];
    }
    return $arr;
}

displayXGroupedByY($arr, 'name', 'city');

Answer 5

user defined sorting should do a work:

http://us2.php.net/manual/en/function.uasort.php