Passing arrays as url parameter

There is a very simple solution: http_build_query(). It takes your query parameters as an associative array:

$data = array(
    1,
    4,
    'a' => 'b',
    'c' => 'd'
);
$query = http_build_query(array('aParam' => $data));

will return

string(63) "aParam%5B0%5D=1&aParam%5B1%5D=4&aParam%5Ba%5D=b&aParam%5Bc%5D=d"

http_build_query() handles all the necessary escaping for you (%5B => [ and %5D => ]), so this string is equal to aParam[0]=1&aParam[1]=4&aParam[a]=b&aParam[c]=d.

Edit: Don't miss Stefan's solution above, which uses the very handy http_build_query() function: https://stackoverflow.com/a/1764199/179125

knittl is right on about escaping. However, there's a simpler way to do this:

$url = 'http://example.com/index.php?';
$url .= 'aValues[]=' . implode('&aValues[]=', array_map('urlencode', $aValues));

If you want to do this with an associative array, try this instead:

PHP 5.3+ (lambda function)

$url = 'http://example.com/index.php?';
$url .= implode('&', array_map(function($key, $val) {
    return 'aValues[' . urlencode($key) . ']=' . urlencode($val);
  },
  array_keys($aValues), $aValues)
);

PHP <5.3 (callback)

function urlify($key, $val) {
  return 'aValues[' . urlencode($key) . ']=' . urlencode($val);
}

$url = 'http://example.com/index.php?';
$url .= implode('&', array_map('urlify', array_keys($aValues), $aValues));