Preg match array keys - php

Question

I have it like this:
$data = array(
"City_0" => "London",
"City_1" => "Paris",
"City_2" => "Lisbon",
"City_3" => "Berlin"
);
plus some other data in that same array.
User will select only one of these and what I need is:
Check with preg_match to get all keys that starts with "city_"
find key which has value (it is not empty), take that value
assign it to new key
remove all "city_" keys
add new key to array with the name "chosen_city" which will contain that value
What I tried:
foreach ($data as $key => $value) {
$matches = preg_match('/city_/i', $key);
if ($value != "") {
$newValue = $value;
break;
}
}
$data['chosen_city'] = $newValue;
print_r($data);
This works partially, how can I remove all previous "city_" keys from array in that if statement?
NOTE:
I have other keys in array, and I don't want to remove them as well.
Input array:
$data = array(
"City_0" => "London",
"City_1" => "Paris",
"City_2" => "Lisbon",
"City_3" => "Berlin",
"distance" => "5 km",
"days" => "7",
"tickets" => "2",
"discount" => "10%",
);
Expected output:
$data = array(
"chosen_city" => "Berlin",
"distance" => "5 km",
"days" => "7",
"tickets" => "2",
"discount" => "10%",
);
Thanks.

Answer 1

Please put unset for example code :
$data = array( "City_0" => "London", "City_1" => "Paris", "City_2" => "Lisbon", "City_3" => "Berlin");
foreach($data as $key => $value){
$matches = preg_match('/city_/i', $key);
if($matches && $value != ""){
$newValue = $value;
unset($data[$key]);
}elseif($matches){
unset($data[$key]);
}
}
$data['chosen_city'] = $newValue;

Answer 2

preg_* is somewhat overkill in this instance - you could use strpos and it'd work just as well
However, the question is 'how to I remove the city_* keys', so to do that, just use unset():
foreach($data as $key => $value){
$matches = preg_match('/city_/i', $key);
if($value != ""){
$newValue = $value;
unset($data[$key]); //Remove this item from the array
break;
}
}
$data['chosen_city'] = $newValue;
print_r($data);

Answer 3

$data = array(
"City_0" => "London",
"City_1" => "Paris",
"City_2" => "Lisbon",
"City_3" => "Berlin",
"distance" => "5 km",
"days" => "7",
"tickets" => "2",
"discount" => "10%",
);
$value = 'Berlin';
if (array_search($value, $data)) {
$data['chosen_city'] = $value;
foreach ($data as $key=>$val) {
if (stripos($key, 'city_')===0) {
unset($data[$key]);
}
}
}
result:
array(5) {
'distance' =>
string(4) "5 km"
'days' =>
string(1) "7"
'tickets' =>
string(1) "2"
'discount' =>
string(3) "10%"
'chosen_city' =>
string(6) "Berlin"
}
If you use PHP >=5.6, probably you can use (I didn't tested this code)
$city = array_search($value, $data);
if ($city) {
$data['chosen_city'] = $value;
$data = array_filter($data,function($key,$val){return stripos($key,'city_')===false;},ARRAY_FILTER_USE_BOTH);
}