=>在php中使用数组时的含义是什么[复制]

I have a php code.

$metadata = Array(
        'facebook'  => Array(
                'title'         => 'og:title',
                'type'          => 'og:type',
                'url'           => 'og:url',
                'thumbnail'     => 'og:image',
                'sitename'      => 'og:site_name',
                'key'           => 'fb:admins',
                'description'   => 'og:description'
            ),
        'google+'   => Array(
                'thumbnail'     => 'image',
                'title'         => 'name',
                'description'   => 'description'
            ),
        'twitter'   => Array(
                'card'          => 'twitter:card',
                'url'           => 'twitter:url',
                'title'         => 'twitter:title',
                'description'   => 'twitter:description',
                'thumbnail'     => 'twitter:image'
            )
    );

what does the => means. How to access an element in this array.

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You have a multi dimensional array, so facebook, google and twitter are elements of the 1st dimension of the $metadata array and they are arrays themselves, here lies the multi dimension.

The => is just like an arrow pointing to the value/data.

To access the 1st dimension would be $metadata['twitter']; or $metadata[2]; it's the same statement, this would bring back the elements/keys of the twitter array.

To access the 2nd dimension would be $metadata['twitter']['card']; or $metadata[2][0]; again the two statements are the same, this would bring back the value of the element/key card

1. what does the => means.

   As documented under Arrays:

   An array in PHP is actually an ordered map. A map is a type that associates values to keys.

   [ deletia ]

   An array can be created using the array() language construct. It takes any number of comma-separated key => value pairs as arguments.

   array(
       key  => value,
       key2 => value2,
       key3 => value3,
       ...
   )
   

2. How to access an element in this array.

   As documented under Accessing array elements with square bracket syntax:

   Array elements can be accessed using the array[key] syntax.

   Example #6 Accessing array elements

   <?php
   $array = array(
       "foo" => "bar",
       42    => 24,
       "multi" => array(
            "dimensional" => array(
                "array" => "foo"
            )
       )
   );
   
   var_dump($array["foo"]);
   var_dump($array[42]);
   var_dump($array["multi"]["dimensional"]["array"]);
   ?>
   

   The above example will output:

   string(3) "bar"
   int(24)
   string(3) "foo"