How to Retrieve All Values for Duplicate URL Parameters in PHP?

Retrieving Multiple Parameters with Same Name from a URL in PHP

Problem:

When URLs contain multiple parameters with the same name, the PHP $_GET variable returns only the last value. This can be problematic, especially when the application requires access to all values for a given key.

Solution:

To retrieve all values for a given key, the following code can be used:

$query  = explode('&', $_SERVER['QUERY_STRING']);
$params = array();

foreach( $query as $param )
{
  // prevent notice on explode() if $param has no '='
  if (strpos($param, '=') === false) $param += '=';

  list($name, $value) = explode('=', $param, 2);
  $params[urldecode($name)][] = urldecode($value);
}

This code:

• Explodes the query string into individual key-value pairs.
• Decodes key and value names.
• Initializes an associative array $params to store values.
• Adds or appends values to the corresponding key in the $params array.

Result:

Executing this code on the provided URL parameters produces the following array:

array(
  'ctx_ver'     => array('Z39.88-2004'),
  'rft_id'      => array('info:oclcnum/1903126', 'http://www.biodiversitylibrary.org/bibliography/4323'),
  'rft_val_fmt' => array('info:ofi/fmt:kev:mtx:book'),
  'rft.genre'   => array('book'),
  'rft.btitle'  => array('At last: a Christmas in the West Indies.'),
  'rft.place'   => array('London'),
  'rft.pub'     => array('Macmillan and co.'),
  'rft.aufirst' => array('Charles'),
  'rft.aulast'  => array('Kingsley'),
  'rft.au'      => array('Kingsley, Charles'),
  'rft.pages'   => array('1-352'),
  'rft.tpages'  => array('352'),
  'rft.date'    => array('1871')
)

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