PHP sort function, multidimensional array

Question

The code below works and results in a multidimensional array sorted from lowest to highest gas proportion value

usort($BMEnergyArray, function($a, $b) {
              return $a['gasproportion'] - $b['gasproportion'];
              });

However, I need to call this function by passing a variable as the sort parameter, as below, which fails to sort correctly

$energyproportion = "'gasproportion'";

usort($BMEnergyArray, function($a, $b) {
              return $a[$energyproportion] - $b[$energyproportion];
              });

How do I achieve the sort using the variable?

Each item in the array is structured as below:

Array ( [0] => Array ( [time] => 2018-11-01 01:40:00 [gas] => 13159 [coal] => 503 [nuclear] => 5822 [wind] => 2499 [hydro] => 263 [biomass] => 3024 [solar] => 0 [gasproportion] => 52 [coalproportion] => 2 [nuclearproportion] => 23 [windproportion] => 10 [hydroproportion] => 1 [biomassproportion] => 12 [solarproportion] => 0 )

Nigel Ren · Accepted Answer · 2018-11-01 14:36:14Z

3

You can give it access by the function() use() syntax...

$energyproportion = "gasproportion";

usort($BMEnergyArray, function($a, $b) use ($energyproportion) {
              return $a[$energyproportion] - $b[$energyproportion];
              });

edited Nov 1, 2018 at 14:36

answered Nov 1, 2018 at 14:32

Nigel Ren

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