如何从PHP中的关联数组访问特定键？

I'm a newbie to this associative array concept in PHP. Now I'm having an array named $sample as follows:

Array
(
  [name] => definitions
  [text] => 
  [attributes] => Array
  (
    [name] => Mediation_Soap_Server_Reporting
    [targetnamespace] => https://mediation.moceanmobile.net/soap/reporting
  )
  [children] => Array
  (
    [types] => Array
    (
      [0] => Array
      (
        [name] => types
        [text] => 
        [attributes] => Array
        (
        )
        [children] => Array
        (
          [xsd:schema] => Array
          (
            [0] => Array
            (
              [name] => schema
              [text] => 
              [attributes] => Array
              (
                [targetnamespace] => https://mediation.moceanmobile.net/soap/reporting
              )
              [children] => Array
              (
                [xsd:complextype] => Array
                (
                  [0] => Array
                  (
                    [name] => complextype
                    [text] => 
                    [attributes] => Array
                    (
                      [name] => Mediation_Soap_FaultMessage
                    )
                    [children] => Array
                    (
                      [xsd:sequence] => Array
                      (
                        [0] => Array
                        (
                          [name] => sequence
                          [text] => 
                          [attributes] => Array
                          (
                          )
                        )
                      )
                    )
                  )
                )
              )
            )
          )
        )
      )
    )
  )
)

From the above array I want to refer(or access) to the key xsd:schema. But I'm not able to do it. Can you please tell me how should I access or refer this key from the associative array names $sample? Thanks in advance.

To access this value you would use:-

$sample['children']['types'][0]['children']['xsd:schema'];

If you have multiple of these elements in your types array you will need to loop through them:-

foreach($sample['children']['types'] as $type) {
   if(isset($type['children']) && isset($type['children']['xsd:schema'])) {

       // Perform action on element
       $type['children']['xsd:schema'];

   }
}

If you do not know your structure (as in xsd:schema can occur outside of types) then you will need to write a recursive function or loop for finding it.

I guess your goal is to seek for the key/value pair where the key is "xsd" ?

If so, in PHP, you can do so by using the follwing logic:

while (list($key, $value) = each($arr)) {
    echo "Key: $key; Value: $value<br />
";
}
// OR
foreach ($arr as $key => $value) {
    echo "Key: $key; Value: $value<br />
";
}

Just add a set of recursing or nested loops to traverse the structure until you find the proper key.