Few ways to convert values to negative
<?php
// Multiplying by "-1"
$v = -1 * abs($v);
// Using ternary operator
$v = $v <= 0 ? $v : -$v;
?>
(PHP 4, PHP 5, PHP 7)
abs — Absolute value
numberThe numeric value to process
The absolute value of number. If the
argument number is
of type float, the return type is also float,
otherwise it is integer (as float usually has a
bigger value range than integer).
Example #1 abs() example
<?php
echo abs(-4.2); // 4.2 (double/float)
echo abs(5); // 5 (integer)
echo abs(-5); // 5 (integer)
?>
Few ways to convert values to negative
<?php
// Multiplying by "-1"
$v = -1 * abs($v);
// Using ternary operator
$v = $v <= 0 ? $v : -$v;
?>
[*EDIT* by danbrown AT php DOT net: Merged user's corrected code with previous post content.]
jeremys indicated one thing - there is no sgn function wich actually seems a bit strange for me. Of course it is as simple as possible, but it is usefull and it is a standard math function needed occasionally.
Well, I have solved this function in a bit different matter:
<?php
function sgn($liczba)
{
if($liczba>0)
$liczba=1;
else if($liczba<0)
$liczba=-1;
else if(!is_numeric($liczba))
$liczba=null;
else
$liczba=0;
return $liczba;
}
?>
The difference is that it returns null when the argument isn't a number at all.
If you don't have/want GMP and are working with large numbers/currencies:
<?php
function mb_abs($number)
{
return str_replace('-','',$number);
}
?>
No need to worry about encoding, as your numbers should all be basic (ANSI) strings.