PHP four six in (banker rounding) implementation

In the project to use the bank home rounding method, PHP does not have a ready-made method, so wrote a

function Up6down4 ($num, $n) {    $pow = POW ($n);    $con _a = Floor (Round ($num * $POW * 10,1));    $con _b = Floor (Round ($num * $pow, 1));    $con _c = ($num * $pow *);    $len = strlen (Str_replace ('. ', ' ", $con _c))-strlen ($con _a);//The Loft is 5 && no valid digits after the bit && the former is an even-numbered non-rounding    if (($con _a% 5 = = 0) && bccomp ($con _a, $con _c, ($len)) ==0 && ($con _b% 2 ==0)) {        return floor ($num * $pow)/$pow;    } else{//rounded        return round ($num, $n);}    }

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