Generate URL with parameters from an array

I need to take an array like I have below:

$subids = Array
    (
        [s1] => one
        [s2] => two
        [s3] => three
        [s4] => four
        [s5] => five
        [s6] => six
    )

and generate a URL such as http://example.com?s1=one&s2=two&s3=three=&s4=four&s5=five&s6=six

All of the subids are not always defined, so sometimes s3 may not be defined, so it shouldn't be appended to the URL. Additionally, whatever the first subid is, it has to have the ? preceding it instead of the ampersand (&)

So if the array is just:

$subids = Array
    (
        [s2] => two
        [s6] => six
    )

then the URL needs to be http://example.com?s2=two&s6=six

I have the following so far:

$url = 'http://example.com';

    foreach ($subids AS $key => $value) {
        $result[$id]['url'] .= '&' . $key . '=' . $value;
    }

However, I'm not sure what the best way would be to append the ? at the beginning of the first key/value pair.

I feel like there's a PHP function to help with this but I'm not finding much. I'm using Codeigniter if there's anything I can use that is provided by CI.

All you need is http_build_query:

$final = $url . "?" . http_build_query($subids);

You can use with http_build_query() function. Example from php.net:

<?php
$data = array(
	'foo' => 'bar',
	'baz' => 'boom',
	'cow' => 'milk',
	'php' => 'hypertext processor',
);

echo http_build_query( $data ) . "\n";
echo http_build_query( $data, '', '&amp;' );
?>

And output this lines:

foo=bar&baz=boom&cow=milk&php=hypertext+processor
foo=bar&baz=boom&cow=milk&php=hypertext+processor

You can read from the source: http://www.php.net/manual/en/function.http-build-query.php

BTW, If you use with WordPress, you can this function: http://codex.wordpress.org/Function_Reference/add_query_arg

Have fun. :)

You can use http_build_query() function but be sure to do some validations if the url comes from an external function for example.

$url = getUrlSomewhere();
$params = ['param' => 'value', 'param2' => 'value2'];
$queryParams = http_build_query($params);
if (strpos($url, '?') !== FALSE) {
    $url .= '&'. $queryParams;
} else {
    $url .= '?'. $queryParams;
}

If you have PECL extension you can use http_build_url() which already takes into account if you are adding more parameters to a pre-existent URL or not among other validations it does.