[RESOLVED] getting array key

zzz

If I have an array in the following structure:

$locality = array(

'AZ' => array
(
    'phoenix'     => 'Phoenix'
),

'CA' => array
(
    'la'     => 'Los Angeles',
    'sf'     => 'San Francisco',
    'fresno'     => 'Fresno'
)
);

And the value

$city = 'Los Angeles';

how do I retrieve the key for the city, i.e. la

dagon

foreach()
array_search()

if you check the manual page for the latter I'm sure there are functions for multi d array search

BuzzPHP

<?php
$locality = array( 
  'AZ' => array( 
    'phoenix'     => 'Phoenix' 
  ),        

  'CA' => array ( 
    'la'     => 'Los Angeles', 
    'sf'     => 'San Francisco', 
    'fresno'     => 'Fresno' 
  ) 
); 

$city = 'Los Angeles'; 

foreach ($locality as $state => $value)
  if (($abbreviation = array_search($city, $value)) !== false)
    echo "state=$state abbreviation=$abbreviation name=$city";
?>

Bare in mind that array_search() will be a linear search, so it will be very slow for large tables.

zzz

Perfect! Works great. I've spent good time looking for all recursive search functions.

BuzzPHP

Just on the topic of speed. One simple solution is to swap your key/value structure, so you have the city name as the key.

Then the lookup is very very fast.

Or, you can even do the below, which has both city=>code and code=>city

So, a lookup of either a cityname or code will return the alternate title. But, then this makes the array twice as big.

But, thats the trade off. Memory vs speed has always been an optimization issue.

<?php 
$locality = array( 
  'AZ' => array( 
    'phoenix'=> 'Phoenix', 'Phoenix'=>'phoenix'
  ),         

  'CA' => array ( 
    'la' => 'Los Angeles',  'Los Angeles' => 'la', 
    'sf' => 'San Francisco', 'San Francisco' => 'sf',
    'fresno' => 'Fresno', 'Fresno' => 'fresno'
  ) 
); 

$city = 'Los Angeles'; 

foreach ($locality as $state => $value) if ($altname = $value[$city]) 
    echo "state=$state altname=$altname name=$city"; 
?>

The other idea, is a binary search, but then you need to store the data differently again, since a binary search algorithm requires index keys.

Food for thought