PHP：在数组中查找数组，不进行循环

I have a simple array of boolean arrays as follows:

array(
    array('dog' => true),
    array('cat' => true),
    array('bird' =>false),
    array('fish' => true)
)

How can I find an entry, such as 'cat', without a loop construct? I think I should be able to accomplish this with a php array function, but the solution is eluding me! I just want to know if 'cat' is a valid key - I'm not interested in it's value.

In the example above, 'cat' should return true, while 'turtle' should return false.

$array = array(
  array('dog' => true),
  array('cat' => true),
  array('bird' =>false),
  array('fish' => true)
);

array_walk($array,'test_array');

function test_array($item2, $key){
$isarray =  is_array($item2) ? 'Is Array<br>' : 'No array<br>';
echo $isarray;
}

using array_walk example in the manual

Output:

Is Array
Is Array
Is Array
Is Array

Ideone

This is a ridiculous way of storing keys. There is no point making each key an array by itself if it's going to have just one element.

A much more sensible way of doing what I think you want to do is:

$myArray = array(
    'dog' => true,
    'cat' => true,
    'bird' => false,
    'fish' => true)
)

In which case you could check if a key exists using array_key_exists.

If you have to use the current array structure, then looping is the only way to check.

You could achieve it like this :

1. Reduce your array to a single dimensional array using combination of array_reduce and array_merge PHP functions .
2. In the reduced array , look for the key using array_key_exists .

Your array :

$yourArray = array
(
     array( 'dog' => true )
    ,array( 'cat' => true )
    ,array( 'bird' =>false )
    ,array( 'fish' => true )
);

Code to check if a key exists :

$itemToFind = 'cat'; // turtle

$result =
    array_key_exists
    (
         $itemToFind
        ,array_reduce(
             $yourArray
            ,function ( $v , $w ){ return array_merge( $v ,$w ); }
            ,array()
        )
    );

var_dump( $result );

Code to check if a key exits and to retrieve its value :

$itemToFind = 'cat'; // bird

$result =
    array_key_exists
    (
        $itemToFind
        ,$reducedArray = array_reduce(
            $yourArray
            ,function ( $v , $w ){ return array_merge( $v ,$w ); }
            ,array()
        )
    ) ?$reducedArray[ $itemToFind ] :null;

var_dump( $result );

Using PHP > 5.5.0

You could use combination of array_column and count PHP functions to achieve it :

Code to check if a key exists :

$itemToFind = 'cat';    // turtle

$result = ( count ( array_column( $yourArray ,'cat' ) ) > 0 ) ? true : false;

var_dump( $result );

The above code tested with PHP 5.5.5 is here