Semi-advanced PHP array - php

Question

So I'm new to Arrays, but I think this should be fairly easy, I just can't wrap my head around it.
I've got an array, that can have a varying amount of keys in it, based on how much input is given by the user.
$array = MY_Class( array(
'type' => 'representatives',
'show_this_many' => '10'
));
easy enough, right?
but I've got 1-4 more keys that could be in it, based on user input. They fill out a form on the first page, and it submits to the second page (which contains the array above).
I need to grab City, State, First, last, based on how many fields the user fills out on the previous page. I can't have blank ones so
$array = MY_Class( array(
'type' => 'representatives',
'show_this_many' => '10',
'city' => '',
'state' => '',
'first' => $_GET['first']
));
won't really work. I need a way to determine which fields have been submitted (preferrably via GET) and build the array that way. so can end up with
$array = MY_Class( array(
'type' => 'representatives',
'show_this_many' => '10',
'state' => $_GET['state'],
'first' => $_GET['first']
));
because state and first had a value while city and last did not.
The first thing that came to mind was something like
$array = MY_Class( array(
'type' => 'representatives',
'show_this_many' => '10',
$constants => $variables
));
//where
$constants = array( //_GET stuff values );
$variables = array( //_GET stuff with values );
// magic method to make it like
// CONSTANTS[0] => VARIABLES[0];
// CONSTANTS[1] => VARIABLES[1];
// so everything is lined up
but I'm not sure how to do it :/

Answer 1

You will want to use a whitelist of possible keys from $_GET so your array doesn't get polluted with spurious (or possibly malicious) keys, and then you can simply append them onto your array with a loop over $_GET.
// Your array is already initialized with some values:
$array = array(
'type' => 'representatives',
'show_this_many' => '10'
);
// Allowed GET keys
$allowed = array('city','state','first');
// Loop over get and add the keys (if allowed)
foreach ($_GET as $key => $value) {
// If the key is allowed and the value isn't blank...
if (in_array($allowed, $key) && !empty($value)) {
$array[$key] = $value;
}
}
// See all the newly added keys...
var_dump($array);
Another option is to just add all the keys to the array, then call array_filter() to remove the blanks.
$array = array(
'type' => 'representatives',
'show_this_many' => '10',
'city' => '',
'state' => '',
'first' => ''
);
// Add values from $_GET, then filter it
$array = array_filter($array, function($val) {
return $val !== '' && !is_null($val);
});

Answer 2

Try the below code
$array = array(
'type' => 'representatives',
'show_this_many' => '10'
);
$fields = array ('city', 'state', 'first');
foreach ($fields as $field) {
if (!empty($_GET[$field])) {
$array[$field] = $_GET[$field]
}
}