Question

How to sum 2D array (matrix) cols in PHP

Answer 1

function sum_matrix_cols($arr, &$cols_sum)
{
    $rows = count($arr);
    $cols = count($arr[0]);
     
    for ($j = 0; $j < $cols; $j++) {
        for ($i = 0; $i < $rows; $i++) 
            $cols_sum[$j] += $arr[$i][$j];
   }
}
 
$arr = array(
    array(11, 32, 13),
    array(20, 80, 990),
);
$cols_sum = array(0,0,0);

sum_matrix_cols($arr, $cols_sum);

 for ($i = 0; $i < 3; $i++) 
      echo $cols_sum[$i] . "<br />\n";
      
 
/*
run:
 
31
112
1003  
    
*/

 

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