PHP在连接键时将嵌套数组转换为单个数组？

这是一个示例数组：

 $foo = array(
           'employer' => array(
                    'name' => 'Foobar Inc',
                    'phone' => '555-555-5555'
                     ),
           'employee' => array(
                    'name' => 'John Doe',
                    'phone' => '555-555-5556',
                    'address' => array(
                           'state' => 'California',
                           'zip' => '90210'
                        )
                    ),
           'modified' => '2009-12-01',
         );

我希望得到这样的结果：

$fooCompressed = array(
             'employer_name' => 'Foobar Inc',
             'employer_phone' => '555-555-5555',
             'employee_name' => 'John Doe',
             'employee_phone' => '555-555-5556'
             'employee_address_state' => 'California',
             'employee_address_zip' => '90210',
             'modified' => '2009-12-01'
             )

我将如何编写递归函数来处理这个问题？

解决方法:

像这样的东西：

function makeNonnestedRecursive(array &$out, $key, array $in){
    foreach($in as $k=>$v){
        if(is_array($v)){
            makeNonnestedRecursive($out, $key . $k . '_', $v);
        }else{
            $out[$key . $k] = $v;
        }
    }
}

function makeNonnested(array $in){
    $out = array();
    makeNonnestedRecursive($out, '', $in);
    return $out;
}

// Example
$fooCompressed = makeNonnested($foo);