PHP custom sort function based on string occurence?

Question

Say I have an arrray:

$arr = array(
  'Animal Dog',
  'Subject Physics',
  'Place Tokyo',
  'Sport Tennis'
);

I want to usort this with the following criteria: if it contains tokyo rank first, if it contains tennis rank second, if it contains dog rank third.

Place Tokyo,
Sport Tennis,
Animal Dog,
Subject Physics

I know I can use stristr to see if the words exist in $a and $b, but I'm clueless on writing the 3 if conditions...

function cmp($a,$b){
 if ( stristr($a,'tokyo') )
  // return what?
}
usort($arr, "cmp")

How would I go about writing the comparison function?

Answer 1

Try this code.

$arr = array(
    'Animal Dog3',
    'Animal Dog1',
    'Animal Dog2',
    'Subject Physics',
    'Place1 Tokyo',
    'Place4 Tokyo',
    'Sport Tennis'
);

$order_array = array('tokyo', 'tennis', 'dog');
$sort_function = function($a, $b) use($order_array)
        {
        $return = strcasecmp($a, $b);
        foreach ($order_array as $word)
            {
            // if each string contains `tokyo` -- alphabetical order
            if (stripos($a, $word) !== false && stripos($b, $word) !== false)
                {
                $return = strcasecmp($a, $b);
                break;
                }
            // if $a string contains `tokyo` -- $a goes first
            elseif (stripos($a, $word) !== false)
                {
                $return = -1;
                break;
                }
            // if $b string contains `tokyo` -- $b goes first
            elseif (stripos($b, $word) !== false)
                {
                $return = 1;
                break;
                }
            // if $a and $b does not contains -- lets take `tennis`
            else
                {
                continue; // just for readablity
                }
            }
        return $return;
        };

usort($arr, $sort_function);
var_dump($arr);
// ["Place1 Tokyo","Place4 Tokyo","Sport Tennis","Animal Dog1","Animal Dog2","Animal Dog3","Subject Physics"]

Or this one

$arr = array(
    'Animal Dog3',
    'Animal Dog1',
    'Animal Dog2',
    'Subject Physics',
    'Place1 Tokyo',
    'Place4 Tokyo',
    'Sport Tennis'
);
$order_array = array('tokyo', 'tennis', 'dog');
$sort_function = function($a, $b) use($order_array)
        {
        $a_index = sizeof($order_array); // lets suppose that it's last
        $b_index = sizeof($order_array); // lets suppose that it's last
        $i = 0;
        foreach ($order_array as $word)
            {
            if (stripos($a, $word) !== false)
                $a_index = $i;           // remeber index order of $a
            if (stripos($b, $word) !== false)
                $b_index = $i;           // remeber index order of $b
            $i++;
            }

        if ($a_index == $b_index)      // if indexes are equal
            return strcasecmp($a, $b); // alphabetical order
        else
            return $a_index - $b_index; // index order
        };

usort($arr, $sort_function);
var_dump($arr);
// ["Place1 Tokyo","Place4 Tokyo","Sport Tennis","Animal Dog1","Animal Dog2","Animal Dog3","Subject Physics"]

Answer 2

what a strange question.. does this do what you're looking for?

usort($arr, 'cmp');
function cmp($a, $b) {
    $av = (stripos($a, 'tokyo') !== false) * 4 | (stripos($a, 'tennis') !== false) * 2 | (stripos($a, 'dog') !== false);
    $bv = (stripos($b, 'tokyo') !== false) * 4 | (stripos($b, 'tennis') !== false) * 2 | (stripos($b, 'dog') !== false);
    return $av < $bv;
}