How get value for unchecked checkbox in checkbox elements when form posted?

First way - hidden fields (disadvantage: the user can manipulate the value of the field (but one can manipulate the value of the checkbox too, so it's not really a problem, if you only expect 1 or 0))

<form action="" method="post">
<input type="hidden" name="status_1" value="0" />
<input type="checkbox" id="status_1" name="status_1" value="1" />
<input type="hidden" name="status_2" value="0" />
<input type="checkbox" id="status_2" name="status_2" value="1" />
<input type="hidden" name="status_3" value="0" />
<input type="checkbox" id="status_3" name="status_3" value="1" />
<input type="submit" />
</form>
<?php
var_dump($_POST);
/*
 * checking only the second box outputs:
 * 
 * array (size=3)
  'status_1' => string '0' (length=1)
  'status_2' => string '1' (length=1)
  'status_3' => string '0' (length=1)
 */

Second way - to assign default value for non-set indexes:

<form action="" method="post">
<input type="checkbox" id="status_1" name="status_1" value="1" />
<input type="checkbox" id="status_2" name="status_2" value="1" />
<input type="checkbox" id="status_3" name="status_3" value="1" />
<input type="submit" />
</form>
<?php
for($i = 1; $i<=count($_POST); $i++) {
    $_POST["status_$i"] = isset($_POST["status_$i"]) ? $_POST["status_$i"] : 0;
}
var_dump($_POST);

/**
 * Here we will be checking only the third checkbox:
 * 
 * array (size=3)
  'status_3' => string '1' (length=1)
  'status_1' => int 0
  'status_2' => int 0
 */

I think adding hidden fields like this will work

<input type="hidden" id="status_1_" name="status_1"  value="0">
<input type="checkbox" id="status_1" name="status_1" value="1" />

<input type="hidden" id="status_2_" name="status_2" value="0">
<input type="checkbox" id="status_2" name="status_2" value="1" />

<input type="hidden" id="status_3_" name="status_3" value="0">
<input type="checkbox" id="status_3" name="status_3" value="1" />

I thinks it impossible to get array like what you want from html forms. But this some tricks can be used:

$defaultForm = array(
'status_1' => 0,
'status_2' => 0,
'status_3' => 0, 
);

// example array from $_POST
$form = array(
'status_1' => 1,
'status_3' => 1, 
);

$form = array_merge($defaultForm, $form);

Result:

array(3) {

'status_1' => int(1)
'status_2' => int(0)
'status_3' => int(1)

}

Try this. If the checkbox is not checked, then the hidden field with the same name will be passed instead.

<form action="" method="post">
  <input type="hidden" id="hidden_status_1" name="status_1" value="0" />
  <input type="checkbox" id="status_1" name="status_1" value="1" />
  <input type="hidden" id="hidden_status_2" name="status_2" value="0" />
  <input type="checkbox" id="status_2" name="status_2" value="1" />
  <input type="hidden" id="hidden_status_3" name="status_3" value="0" />
  <input type="checkbox" id="status_3" name="status_3" value="1" />
</form>