I have a variable that dynamically receives from the database, a floating number that is the percentage to be taken out of a given value. How do I get this percentage out of a value?
For example:
$total = 4000;
$pctm = 30.00;
$valor_descontado = $total-$pctm.'%';
But that does not work.
This is basic math. To calculate a percentage, divide by 100 and multiply by the percentage you want.
$total = 4000;
$pctm = 30.00;
$valor_descontado = $total - ($total / 100 * $pctm); //os parenteses são desnecessários
See running on ideone .
Of course we are talking about monetary values and there you have another problem .
Just do a simple calculation.
$valor_descontado = $total - $total * $pctm / 100.0;
Considering that:
30% = 30/100
Just use 3:
function porcentagem_nx ( $parcial, $total ) {
return ( $parcial * 100 ) / $total;
}
With this function it will facilitate the calculation of percentage, to use it suffices:
porcentagem_nx(20, 100); // 20
I usually do this to capture the result of a discount:
$total = 4000;
$pctm = 30.00;
$valor_com_desconto = $total - (($total * $pctm) / 100);
echo $valor_com_desconto;
Obs: Mathematics always performs multiplication after division. In this example the logic is separated.
You can also do this as follows:
$total = 4000
$pctm = 30.00
$valor_com_desconto = $total - ($pctm * 0.01)
Another way is by multiplication factor, for example:
If a product has increased 30% then its multiplication factor is 1 + increase rate, this rate being 0.3. Therefore, its multiplication factor is 1.3.
If a product has a discount of 30% then its multiplication factor is 1 - rate of decrease, this rate being 0.3. Therefore, its multiplication factor is 0.7.
$total = 4000;
$pctm = -30.00;//desconto de 30%
echo "Com desconto: " . $total * (1+($pctm/100));
echo PHP_EOL;
$pctm = 30.00;//acréscimo de 30%
echo "Com acréscimo: " . $total * (1+($pctm/100));