6
I have a variable that dynamically receives from the database, a floating number that is the percentage to be taken out of a certain value. How do I take this percentage away from a value?
For example:
$total = 4000;
$pctm = 30.00;
$valor_descontado = $total-$pctm.'%';
But that way, it doesn’t work.
18
This is basic math. To calculate percentage is divided by 100 and multiplied by the desired percentage.
$total = 4000;
$pctm = 30.00;
$valor_descontado = $total - ($total / 100 * $pctm); //os parenteses são desnecessários
Behold working in the ideone. And in the repl it.. Also put on the Github for future reference.
Of course we are talking about monetary values and then you have another problem.
8
Just make a simple calculation.
$valor_descontado = $total - $total * $pctm / 100.0;
whereas:
30% = 30/100
8
Just use rules of 3:
function porcentagem_nx ( $parcial, $total ) {
return ( $parcial * 100 ) / $total;
}
With this function will facilitate the percentage calculation, to use enough:
porcentagem_nx(20, 100); // 20
Well remembered +1, the rule of 3.
2
You can also do as follows:
$total = 4000
$pctm = 30.00
$valor_com_desconto = $total - ($total * $pctm * 0.01)
Divide by 100 and multiply by 0.01 gives the same result.
2
I usually do so 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 executes multiplication after division. In this example the logic is separated.
In fact, multiplication and division have the same "importance" in the order of execution, the famous P/E/MD/AS http://pt.wikihow.com/Calcular-uma-Express%C3%A3o-Usando-PEMDAS
2
Another way is by the multiplication factor, example:
If a product increased by 30% then its multiplication factor is 1 + increment rate, this rate being 0.3. Therefore, its multiplication factor is 1.3.
If a product had a 30% discount then its multiplication factor is 1 - decrease rate, 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));
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Resolved, thanks not only to you, but to all.
– Michel Henriq
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– John Quimera
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– John Quimera