PHP 7 - How to search for multiple specific members of an array

Question

I have a PHP array that looks like this:

array (size=3)
  'CA,Santa Barbara' => 
    array (size=2)
      'state' => string 'CA' (length=2)
      'city' => string 'Santa Barbara' (length=13)
  'KS,Andover' => 
    array (size=2)
      'state' => string 'KS' (length=2)
      'city' => string 'Andover' (length=7)
  'KS,Wichita' => 
    array (size=2)
      'state' => string 'KS' (length=2)
      'city' => string 'Wichita' (length=7)

I need to return all the array members who have the values:

state => 'KS'

I am needing to get an array back that looks like this:

array (size=2)
  'KS,Andover' => 
    array (size=2)
      'state' => string 'KS' (length=2)
      'city' => string 'Andover' (length=7)
  'KS,Wichita' => 
    array (size=2)
      'state' => string 'KS' (length=2)
      'city' => string 'Wichita' (length=7)

Is there a PHP array function that does this? I have found array_search() but that only returns the first match. I need ALL matches.

Answer 1

You could use array_filter() to remove all unneeded values:

$array = [
    'CA,Santa Barbara' => ['state' => 'CA', 'city' => 'Santa Barbara'],
    'KS,Andover'       => ['state' => 'KS', 'city' => 'Andover'],
    'KS,Wichita'       => ['state' => 'KS', 'city' => 'Wichita'],
];

$state = 'KS';
$out   = array_filter($array, fn($v) => $v['state'] == $state);
print_r($out);

Outputs:

Array(
    [KS,Andover] => Array(
            [state] => KS
            [city] => Andover
        )
    [KS,Wichita] => Array(
            [state] => KS
            [city] => Wichita
        )
)

You can also use type hinting to get a better data flow control:

$out = array_filter($array, fn(array $v): bool => $v['state'] == $state);
#                              ^          ^
#                              |          |
#                              |          array_filter's callback returns
#                              |          a boolean (true to keep,
#                              |          false to remove).
#                              |
#                              each elements of the $array
#                              are arrays.

Before PHP 7.4, (without arrow functions), you have to use the keyword use to pass the $state variable to the anonymous function:

$state = 'KS';
$out   = array_filter($array, function($v) use ($state) {
    return $v['state'] == $state;
});
print_r($out);