Description:
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the sum of the numbers (positive and negative) in a loop, is expected to be 0

tested with:
PHP 7.3.12-1
PHP 7.0.33-0 (cli) 
PHP 7.3.9 (cli) 

Test script:
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$arr = [1.9, 1.9, 1.9, -5.7]; or  $arr = [1.9, 1.9, 1.9, 1.9, 1.9, 1.9, 1.9, 1.9, -15.2]; or  $arr = [1.9, 1.9, 1.9, 1.9, 1.9, 1.9, 1.9, 1.9, 1.9, 1.9, 1.9, 1.9, -22.8];
echo array_sum($arr);  //-8.8817841970013E-16  //1.7763568394003E-15  //-3.5527136788005E-15

AND same result with
$total = 0; foreach( $arr as $a ){ $total += $a; } echo $total;  // -8.8817841970013E-16  //1.7763568394003E-15  //-3.5527136788005E-15



BUT this works
$arr = [1.9, 1.9, -3.8];  //0
$arr = [1.9, 1.9, 1.9, 1.9, -7.6];  //0
$arr = [1.9, 1.9, 1.9, 1.9, 1.9, 1.9, 1.9, 1.9, 1.9, -17.1];  //0