PHP usort Array of Objects Against External Variable

Question

I hope this is not a duplicate question; I have searched to no avail...

I am trying to sort an array of objects returned by a search. I want to sort the results as follows: If the "name" property of an object matches the search query, put it at the top. Next, if the "city" property matches the query, put those next. (I intend to add more criteria later.) So I'm not strictly comparing values, but rather comparing each object $a to the search query $q. The array is indeed being re-indexed, but not in the order I am expecting. What am I missing?

function cmp($a, $b) {
    global $q; // search query

    $query = strtolower($q);
    $name  = strtolower($a->getName()); // defined in class
    $city  = strtolower($a->getCity()); // defined in class

    if ($name == $query) {
      return -1;
    }

    elseif ($city == $query) {
       return -1;
    }

    return 0;
}

usort($cinemas, 'cmp'); // $cinemas is an array of objects

the cmp function has to return 3 things: less than (-1), equal (0), greater than (+1). you're only returning two things: -1 and 0 — Marc B
– Marc B, Commented Sep 3, 2014 at 18:40
Hmm... I tried adding another elseif returning 1, but the results are still ordered in the same way (matching city is not at the top). — Mike F
– Mike F, Commented Sep 3, 2014 at 18:56
Would you please give an example of your 'search query' array. i.e. array('name' => 'fred', 'city' => 'mycity') or is it a different format? Some sample data and expected results may be useful. Your comment 'matching city is not at the top' - I am not sure how that would come about. — Ryan Vincent
– Ryan Vincent, Commented Sep 3, 2014 at 19:01
Way over-simplified, but something like this. $cinemas: Array ( [0] => Cinema Object ( [name:protected] => Sample One [city:protected] => Grapevine ) [1] => Cinema Object ( [name:protected] => Sample Two [city:protected] => Flower Mound ) [2] => Cinema Object ( [name:protected] => Sample Three [city:protected] => TROPHY CLUB ) [3] => Cinema Object ( [name:protected] => Sample Four [city:protected] => Irving ) ) — Mike F
– Mike F, Commented Sep 3, 2014 at 19:24
And $q is a sanitized version of what the user typed in the search input. — Mike F
– Mike F, Commented Sep 3, 2014 at 19:27

deceze · Accepted Answer · 2014-09-03 20:03:00Z

1

You need to compare two items in your comparison function and return which one is greater. At the moment you're completely ignoring the second item being passed in, $b. Your logic needs to be, in this order:

if both a's and b's name match the query, they're equal
if a's name matches the query, it is greater
if b's name matches the query, it is greater
if both a's and b's city match the query, they're equal
if a's city matches the query, it is greater
if b's city matches the query, it is greater
if a's name and b's name aren't equal, return the strcmp value of both
return the strcmp value of a's city and b's city

answered Sep 3, 2014 at 20:03

deceze♦

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lxg · Accepted Answer · 2014-09-03 21:26:15Z

0

You should use an anonymous function:

usort($cinemas, function($a, $b) use ($q) {
    $query = strtolower($q);
    $name  = strtolower($a->getName()); // defined in class
    $city  = strtolower($a->getCity()); // defined in class

    // do the comparison
});

Note that $q was imported into the scope of the function, so there's no need for a global.

Apart from that, the function should return either 1, 0 or -1, as has been mentioned in the comments on the question.

edited Sep 3, 2014 at 21:26

answered Sep 3, 2014 at 19:46

lxg

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2 Comments

Ryan Vincent Over a year ago

The 'usort' function need to return one of 'three' values: -1 for 'less than', +1 for 'greater than; and zero for 'equal to'.

lxg Over a year ago

Thanks, fixed. (Although, in reality, -1 and 1 are usually sufficient.)

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