php - Array parts access -


i'm trying understand arrays better. pardon elementary questions opened first php book 3 weeks ago.

i can retrieve key/value pairs using foreach (or loop) below.

 $stockprices= array("google"=>"800", "apple"=>"400", "microsoft"=>"4",  "rim"=>"15",  "facebook"=>"30");  foreach ($stockprices $key =>$price)

what confused multi dimensional arrays one:

$states=(array([0]=>array("capital"=> "sacramento", "joined_union"=>1850, "population_rank"=> 1),               [1]=>array("capital"=> "austin", "joined_union"=>1845,"population_rank"=> 2),               [2]=>array("capital"=> "boston", "joined_union"=>1788,"population_rank"=> 14)               ));

my first question basic: know "capital', "joined_union", "population_rank" keys , "sacramento", "1850", "1" values (correct?). call [0][1][2]? "main keys" , "capital" etc. sub-keys? can't find definition those; neither in books nor online.

the main question how retrieve arrays [0][1][2]? want array joined_union in 1845 (or trickier during 1800s), remove array.

finally, can name arrays [0][1][2] california, texas , massachusetts correspondingly?

$states=(array("california"=>array("capital"=> "sacramento", "joined_union"=>1850, "population_rank"=> 1),               "texas"=>array("capital"=> "austin", "joined_union"=>1845,"population_rank"=> 2),               "massachusetts"=>array("capital"=> "boston", "joined_union"=>1788,"population_rank"=> 14)               ));

unlike other languages, arrays in php can use numeric or string keys. choose. (this not loved feature of php , other languages sneer!)

$states = array(     "california"    => array(         "capital"         => "sacramento",         "joined_union"    => 1850,         "population_rank" => 1     ),     "texas"         => array(         "capital"         => "austin",         "joined_union"    => 1845,         "population_rank" => 2     ),     "massachusetts" => array(         "capital"         => "boston",         "joined_union"    => 1788,         "population_rank" => 14     ) );

as querying structure have, there 2 ways
1) looping

$joined1850_loop = array(); foreach( $states $statename => $statedata ) {     if( $statedata['joined_union'] == 1850 ) {         $joined1850_loop[$statename] = $statedata;     } } print_r( $joined1850_loop ); /* array (     [california] => array         (             [capital] => sacramento             [joined_union] => 1850             [population_rank] => 1         )  ) */

2) using array_filter function: 

$joined1850 = array_filter(     $states,     function( $state ) {         return $state['joined_union'] == 1850;     } ); print_r( $joined1850 ); /* array (     [california] => array         (             [capital] => sacramento             [joined_union] => 1850             [population_rank] => 1         )  ) */

-

$joined1800s = array_filter(     $states,     function ( $state ){         return $state['joined_union'] >= 1800 && $state['joined_union'] < 1900;     } ); print_r( $joined1800s ); /* array (     [california] => array         (             [capital] => sacramento             [joined_union] => 1850             [population_rank] => 1         )      [texas] => array         (             [capital] => austin             [joined_union] => 1845             [population_rank] => 2         )  ) */

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