array of floats use in php

Question

In order to draw my chart, I need to have 2 arrays of floats,

1. The first one stores in MySQL database as a type of string (separated by commas)
2. And I want to define the second one as a constant array (in PHP)

my problem is how to change the type of data as string(MySQL) and use it as arrays of float in PHP. Also, how should I define the second array? Should I change it to string and then use unserialize?

This just print 1

$data = array();
$data['cols'] = array(
    array('id' => 'Signal','label' => 'Signal', 'type' => 'string'));

$rows = array();
while($r = mysql_fetch_assoc($result)) {
  $temp = array();
  $temp[] = array('v' => $r['Signal']); 
  $res = array_map("floatval", $temp);

  var_dump($res);}                                 

echo var_dump($res);

Answer 1

You can use a combination of floatval() and array_map() to parse your string array into a float array.

A simple tested example:

$input_array = Array("1.1234", "3.123", "2.23E3", "2.23E-3");

$result = array_map("floatval", $input_array);

var_dump($input_array);
var_dump($result);

Prints:

array(4) {
  [0]=> string(6) "1.1234"
  [1]=> string(5) "3.123"
  [2]=> string(6) "2.23E3"
  [3]=> string(7) "2.23E-3"
}
array(4) {
  [0]=> float(1.1234)
  [1]=> float(3.123)
  [2]=> float(2230)
  [3]=> float(0.00223)
}

P.S.: If your database result is somewhat more structured than just a flat array of float-valued strings, you might need to do more than just map it. Provide some more info on what you have and what you expect for more detailed help.

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As for your second array, I'm afraid you can't mark arrays as constant. Here is a relevant question. You can go into classes and autosetters, but I'm not sure that kind of complexity is justified for your requirements.