How to choose the highest value of an array?

Question

I’m trying to use the function max, but I can’t hit.

// variáveis da diferença salarial 
$saldev[0] = $_POST ["Tdate5"];
$saldev[1] = $_POST ["Tdate9"];
$saldev[2] = $_POST ["Tdate13"];
$saldev[3] = $_POST ["Tdate17"];
$saldev[4] = $_POST ["Tdate21"];

$saldev2 = max($saldev);

(Note: The above code works the way it is. Due to a inexplicable error I received some wrong outputs and created the question, and from some tips I found that it was working (ok, it’s confusing, but what matters is that it’s working). The hypothesis with ksortalso works for the same purpose, so I chose it as solved)

But the exit from var_dump of $saldev after sending the form with the completed fields, is:

array(5) { [0]=> string(0) "" 1=> string(0) "" [2]=> string(0) "" [3]=> string(0) "" [4]=> string(0) "" }

And that of $saldev2 is:

string(0) ""

The HTML of form is within a large table, I will include one of the fields input (everyone is like that):

<label for="Cvpos5"></label>
<input type="text" id="Cvpos5" name="Tdate5" size="10" class="preco"> 

Answer 1

There is a function to sort an array by keys in descending order - krsort

Use krsort to sort the array downwards and just use Current to retrieve the first element, because krsort maintains the correlation between the keys and the values.

$saldev[] = 'Tdate5';
$saldev[] = 'Tdate9';
$saldev[] = 'Tdate13';
$saldev[] = 'Tdate17';
$saldev[] = 'Tdate21';

krsort($saldev);
echo current( $saldev );

_Output:

Tdate21

Answer 2

The function max expects to receive an array of numbers, so do so:

$saldev[0] = (double) $_POST ["Tdate5"];
$saldev[1] = (double) $_POST ["Tdate9"];
$saldev[2] = (double) $_POST ["Tdate13"];
$saldev[3] = (double) $_POST ["Tdate17"];
$saldev[4] = (double) $_POST ["Tdate21"];

$saldev2 = max($saldev);

Answer 3

There is a space in your line, the bracket should "touch" the variable:

$saldev[0] = $_POST["Tdate5"];

Also, make sure the form contains method="post" or it will send the data by GET. When sent by GET the values are accessible via something like $_GET["Tdate5"], that besides being less recommended in most cases would not work ever using $_POST.

Example:

<form method="post">

If it still doesn’t work, post the form and the Urls used, but in my experience this should solve..