I am having trouble trying to pass an extra variable in the url to my WordPress installation.
For example /news?c=123
For some reason, it works only on the website root but it does not work if the url contains any more information . I have the following code in my functions.php file in the theme directory.
if (isset($_GET['c']))
{ setcookie("cCookie", $_GET['c']);
}
if (isset($_SERVER['HTTP_REFERER']))
{ setcookie("rCookie", $_SERVER['HTTP_REFERER']);
}Any Ideas?
19 Answers
To make the round trip "The WordPress Way" on the "front-end" (doesn't work in the context of wp-admin), you need to use 3 WordPress functions:
- add_query_arg() - to create the URL with your new query variable ('c' in your example)
- the query_vars filter - to modify the list of public query variables that WordPress knows about (this only works on the front-end, because the WP Query is not used on the back end -
wp-admin- so this will also not be available inadmin-ajax) - get_query_var() - to retrieve the value of your custom query variable passed in your URL.
Note: there's no need to even touch the superglobals ($_GET) if you do it this way.
Example
On the page where you need to create the link / set the query variable:
if it's a link back to this page, just adding the query variable
<a href="<?php echo esc_url( add_query_arg( 'c', $my_value_for_c ) )?>">
if it's a link to some other page
<a href="<?php echo esc_url( add_query_arg( 'c', $my_value_for_c, site_url( '/some_other_page/' ) ) )?>">
In your functions.php, or some plugin file or custom class (front-end only):
function add_custom_query_var( $vars ){ $vars[] = "c"; return $vars;
}
add_filter( 'query_vars', 'add_custom_query_var' );On the page / function where you wish to retrieve and work with the query var set in your URL:
$my_c = get_query_var( 'c' );
On the Back End (wp-admin)
On the back end we don't ever run wp(), so the main WP Query does not get run. As a result, there are no query vars and the query_vars hook is not run.
In this case, you'll need to revert to the more standard approach of examining your $_GET superglobal. The best way to do this is probably:
$my_c = filter_input( INPUT_GET, "c", FILTER_SANITIZE_STRING );
though in a pinch you could do the tried and true
$my_c = isset( $_GET['c'] ? $_GET['c'] : "";
or some variant thereof.
7There are quite few solutions to tackle this issue. First you can go for a plugin if you want:
Or code manually, check out this post:
Also check out:
Since this is a frequently visited post i thought to post my solution in case it helps anyone. In WordPress along with using query vars you can change permalinks too like this
to For this you have to add these lines of code in functions.php or your plugin base file.
From shankhan's anwer
add_filter( 'query_vars', 'addnew_query_vars', 10, 1 );
function addnew_query_vars($vars)
{ $vars[] = 'c'; // c is the name of variable you want to add return $vars;
}And additionally this snipped to add custom rewriting rules.
function custom_rewrite_basic()
{ add_rewrite_rule('^c/([0-9]+)/?', '?c=$1', 'top');
}
add_action('init', 'custom_rewrite_basic');For the case where you need to add rewrite rules for a specifc page you can use that page slug to write a rewrite rule for that specific page. Like in the question OP has asked about
to We can change it to the desired behaviour by adding a little modification to our previous function.
function custom_rewrite_basic()
{ add_rewrite_rule('^news/([0-9]+)/?', 'news?c=$1', 'top');
}
add_action('init', 'custom_rewrite_basic');Hoping that it becomes useful for someone.
5add following code in function.php
add_filter( 'query_vars', 'addnew_query_vars', 10, 1 );
function addnew_query_vars($vars)
{ $vars[] = 'var1'; // var1 is the name of variable you want to add return $vars;
}then you will b able to use $_GET['var1']
<?php
$edit_post = add_query_arg('c', '123', 'news' );
?>
<a href="<?php echo $edit_post; ?>">Go to New page</a>You can add any page inplace of "news".
One issue you might run into is is_home() returns true when a registered query_var is present in the home URL. For example, if displays a static page instead of the blog, will return the blog.
See and for more info on this.
What you can do (if you're not attempting to affect the query) is use add_rewrite_endpoint(). It should be run during the init action as it affects the rewrite rules. Eg.
add_action( 'init', 'add_custom_setcookie_rewrite_endpoints' );
function add_custom_setcookie_rewrite_endpoints() { //add ?c=123 endpoint with //EP_ALL so endpoint is present across all places //no effect on the query vars add_rewrite_endpoint( 'c', EP_ALL, $query_vars = false );
}This should give you access to $_GET['c'] when the url contains more information like .
Remember to flush your rewrite rules after adding/modifying this.
to add parameter to post urls (to perma-links), i use this:
add_filter( 'post_type_link', 'append_query_string', 10, 2 );
function append_query_string( $url, $post )
{ return add_query_arg('my_pid',$post->ID, $url);
}output:
1This was the only way I could get this to work
add_action('init','add_query_args');
function add_query_args()
{ add_query_arg( 'var1', 'val1' );
}In your case, Just add / after url and then put query arguments. like
or news/?c=123
instead of
or news?c=123
