Sorting array using usort and global variable

Question

I'm using usort to sort a multi-dimensional array. It works fine until the key used to sort concatenates a global variable.

var_dump($lang);//OK, outputs 'eng'

function cmp(array $a, array $b) {
    if ($a['name'] < $b['name']) {
        return -1;
    } else if ($a['name'] > $b['name']) {
        return 1;
    } else {
        return 0;
    }
}

function cmp2(array $a, array $b) {
    global $lang;
    var_dump($lang);//null?

    if ($a['name_'.$lang] < $b['name_'.$lang]) {//line: 93
        return -1;
    } else if ($a['name_'.$lang] > $b['name_'.$lang]) {
        return 1;
    } else {
        return 0;
    }
}

usort($platform['Server'], "cmp");//OK
usort($platform['Asset'], "cmp2");//Notice (8): Undefined index: name_ [APP\View\Platforms\view.ctp, line 93]

How can I concatenate the lang variable inside the function passed to usort?

I'm on PHP 5.3.

Also, would there be a way to unify both these functions into one while passing the key to sort on as a parameter?

What version of PHP are using? If you are using PHP 5.3+, I have a solution for you. — gen_Eric
– gen_Eric, Commented May 1, 2014 at 16:30
As for this code, my guess is that this code is inside a function, so $lang isn't actually global. — gen_Eric
– gen_Eric, Commented May 1, 2014 at 16:31

gen_Eric · Accepted Answer · 2014-05-01 16:32:43Z

11

If you are using PHP 5.3+, then you can take advantage of anonymous functions:

usort($platform['Asset'], function(array $a, array $b) use($lang){
    if ($a['name_'.$lang] < $b['name_'.$lang]) {
        return -1;
    } else if ($a['name_'.$lang] > $b['name_'.$lang]) {
        return 1;
    } else {
        return 0;
    }
});

answered May 1, 2014 at 16:32

gen_Eric

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3 Comments

TechFanDan Over a year ago

thanks for pointing out how to pass $lang to the function, couldn't figure out how I was going to accomplish this... even though a quick search with specific keywords (just learned) seems to yield the same answer you provided. Ah well...

gen_Eric Over a year ago

Here's the docs for it: php.net/manual/en/functions.anonymous.php#example-180 "Closures may also inherit variables from the parent scope. Any such variables must be passed to the use language construct."

dewd Over a year ago

i never knew about use! doh!

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