How to pass an additional variable into a cmp function for use with usort in php

Question

I need to order an array using usort based on a string of text that comes from a mysql call using php4.

So far I have the mysql call to get the order:

$result=mysql_query("SELECT rank from order WHERE id=1");
$row = mysql_fetch_row($result);

this gives me something like $row[0]='Alberto, Carlos, Brocephus, Edgar, Daniela';

And I have the function, which works if I hard code in an array:

function cmp($a,$b){
    //$order = how do I get $row[0] in here?
    $a_index = array_search($a['name'], $order);
    if (!$a_index) {
        $a_index = 999;
    }
    $b_index = array_search($b['name'], $order);
    if (!$b_index) {
        $b_index = 999;
    }
    return $a_index - $b_index;
}
usort($names,cmp);

What's the simplest way to get that string into the cmp function as an array?

http://php.net/manual/en/function.usort.php look at example #4 does that help? — Pitchinnate, Apr 03 '13 at 18:29
@Pitchinnate It won't help in his case, as the OP said they were using PHP4 which does not have closures. — Mike Brant, Apr 03 '13 at 18:30

score 4 · Answer 1 · edited Apr 19 '13 at 09:28

You can't use a closure in PHP 4, but you can use an object.

class ArrayComparer {

    var $indexedarray;

    function ArrayComparer($str) {
        $this->indexedarray = array_flip(explode(', ', $str));
    }

    function cmp($a, $b) {
        $a = $a['name'];
        $b = $b['name'];
        $a_index = (isset($this->indexedarray[$a])) ? $this->indexedarray[$a] : 0x7fffffff;
        $b_index = (isset($this->indexedarray[$b])) ? $this->indexedarray[$b] : 0x7fffffff;
        return $a_index - $b_index;
    }

    function callback() {
        return array($this, 'cmp');
    }
}

Example of use:

$cmp = new ArrayComparer('Alberto, Carlos, Brocephus, Edgar, Daniela');
usort($names, $cmp->callback());

score 0 · Answer 2 · answered Apr 03 '13 at 18:29

If you were in a modern version of PHP, you could simply use the use keyword like this:

function cmp($a, $b) use $your_string {
    ...
}

Or use a closure along with use like this:

usort(function($a, $b) use $your_string {
    ...
});

However, since you are working with an ancient version of PHP, you might have to resort to using a global declaration

function cmp($a, $b) {
    global $your_string;
    ...
}

How to pass an additional variable into a cmp function for use with usort in php

2 Answers2