How to change the delimiter of the Php array obtained via POST, replacing the comma?

To really do what you're asking, you can use the preg_match_all and find the appropriate values with a regular expression:

$reference = "2,7 cm, 3,1 cm, 20,0 dm, 0,89 m, 0,0001 km";

if (preg_match_all("/[0-9]+\,[0-9]+ [a-zA-Z]+/", $reference, $matches))
{
  print_r($matches);
}

The output will be:

Array
(
    [0] => Array
        (
            [0] => 2,7 cm
            [1] => 3,1 cm
            [2] => 20,0 dm
            [3] => 0,89 m
            [4] => 0,0001 km
        )

)

Then just do: implode("__", $matches[0]) to have:

2,7 cm__3,1 cm__20,0 dm__0,89 m__0,0001 km 

  

Note that this way the program can also handle different units.

If the data already is in this 2,7 cm, 3,1 cm pattern, and you are sure that this pattern will always remain that way, then you could just use% com_and% as a delimiter so you would not have to change anything in the sending process of the form.

No , would look something like this

$MyArray = explode(", ", array_filter( $_POST['Referencia'] ) );

The array will be

array(
    2,7 cm,
    3,1 cm
)

This seems to be the least invasive and clean way.

It is unclear where you want to modify, whether it is on the pre-submission form or the two sides. Finally, I have chosen to show a solution that is as simple as possible.