Q:

Losing php empty post entries

I have a strange situation in one of my servers. Whenever I post a form that contains an empty value for a given post key, when I try to read that key from the $_POST array it is not set as expected.
I expect:
isset($_POST[$k]) == true

But I get:
isset($_POST[$k]) == false

I have not been able to find evidence of this problem anywhere else in the web.
I have two servers and in one of them it happens and in the other one it does not.
I have no idea if it could related to my version of PHP, or Apache, or some configuration file.
Test scenario:
<?php
    print_r($_POST['param']);
?>
<form action="posttest.php" method="post">
    <input type="text" name="param[text1]" value="1"><br>
    <input type="text" name="param[text2]" value=""><br>
    <input type="text" name="param[text3]" value="3"><br>
    <input type="text" name="param[text4]" value=""><br>
    <input type="text" name="param[text5]" value="4"><br>
    <button type="submit">Send</button>
</form>

Server A (the good one)
Data:

PHP Version 5.4.45

Echoes this:
[param] => Array
(
    [text1] => 1
    [text2] => 
    [text3] => 3
    [text4] => 
    [text5] => 4
)

Server B (the faulty one)
Data:

PHP Version 5.6.20

Echoes this:
[param] => Array
(
    [text1] => 1
    [text3] => 3
    [text5] => 4
)

I don't know what more info to add to the question, so if you have a clue and need more information please let me know and I will update the question

A:

The problem has disappeared and it was after running an EasyApache on my WHM console. Maybe it was a misconfiguration or a bug in the php binary I was using, who knows.

