Title: variable mismatch Last modified: March 2, 2019 --- # variable mismatch * [dapike](https://wordpress.org/support/users/dapike/) * (@dapike) * [7 years, 3 months ago](https://wordpress.org/support/topic/variable-mismatch/) * I have a page that contains a form, into which data can be entered by the user into several fields. When the user clicks on submit, processing goes to PHP code in another page. The form itself is set up with method=”post” * Prior to an automated upgrade to WP 4.9.9 this form worked fine. Subsequent to the upgrade it fails… when the user clicks submit, what is now shown is just the message “A variable mismatch has been detected.” * How can I fix this? Indeed, how can I even debug it and try to find out *which variable* is being detected as having some sort of mismatch. Viewing 15 replies - 1 through 15 (of 18 total) 1 [2](https://wordpress.org/support/topic/variable-mismatch/page/2/?output_format=md) [→](https://wordpress.org/support/topic/variable-mismatch/page/2/?output_format=md) * [Radices](https://wordpress.org/support/users/radices/) * (@radices) * [7 years, 3 months ago](https://wordpress.org/support/topic/variable-mismatch/#post-10993569) * [https://make.wordpress.org/core/2018/12/13/backwards-compatibility-breaks-in-5-0-1/](https://make.wordpress.org/core/2018/12/13/backwards-compatibility-breaks-in-5-0-1/) * Form element no longer passes KSES Prior to 5.0.1, the $allowedposttags array contained an entry for the
element and some of its attributes. Because of that, Contributors and Authors could use it in posts. * The element was removed in 5.0.1, except for situations where a plugin has explicitly registered input or select fields via the wp_kses_allowed_html filter. If a Contributor or Author includes in their post, it will be removed when the post is saved. It will also be stripped from arbitrary content that plugins pass to wp_kses_post() or wp_kses_allowed_html( ‘post’ ). * If a plugin author wants to restore the original behavior, they will need to add form, input or select tags via wp_kses_allowed_html. Please exercise caution when doing so, because this could re-introduce a vulnerability. Make sure only trusted users are allowed to add tags. * Moderator [Steven Stern (sterndata)](https://wordpress.org/support/users/sterndata/) * (@sterndata) * Volunteer Forum Moderator * [7 years, 3 months ago](https://wordpress.org/support/topic/variable-mismatch/#post-10993622) * What plugin are you using for your forms? * Thread Starter [dapike](https://wordpress.org/support/users/dapike/) * (@dapike) * [7 years, 3 months ago](https://wordpress.org/support/topic/variable-mismatch/#post-10993648) * I’m not using any plugin to create the forms. I’ve written the html code for them directly into the page. * Moderator [Steven Stern (sterndata)](https://wordpress.org/support/users/sterndata/) * (@sterndata) * Volunteer Forum Moderator * [7 years, 3 months ago](https://wordpress.org/support/topic/variable-mismatch/#post-10993652) * OK, then see the “make” article posted above. * Thread Starter [dapike](https://wordpress.org/support/users/dapike/) * (@dapike) * [7 years, 3 months ago](https://wordpress.org/support/topic/variable-mismatch/#post-10993658) * So I need to “add form, input or select tags via wp_kses_allowed_html” ?? * Is there an example somewhere that I could look at to show how this gets accomplished? * Thanks, * – David. * Moderator [Steven Stern (sterndata)](https://wordpress.org/support/users/sterndata/) * (@sterndata) * Volunteer Forum Moderator * [7 years, 3 months ago](https://wordpress.org/support/topic/variable-mismatch/#post-10993663) * see [https://codex.wordpress.org/Function_Reference/wp_kses_allowed_html](https://codex.wordpress.org/Function_Reference/wp_kses_allowed_html) and [http://hookr.io/filters/wp_kses_allowed_html/](http://hookr.io/filters/wp_kses_allowed_html/) * Thread Starter [dapike](https://wordpress.org/support/users/dapike/) * (@dapike) * [7 years, 3 months ago](https://wordpress.org/support/topic/variable-mismatch/#post-10993862) * Based on what I’ve read, I think the following PHP code, placed somewhere prior to where the element appears in the html code, ought to restore the functionality of the element: * ``` function my_filter_function_name( $string ) { $string['form'] = array ('class' => array(), 'action' => array(), 'method' => array(), 'style' => array() ); return $string; } add_filter( 'pre_kses', 'my_filter_function_name' ); ``` * But it isn’t working, so evidently I’ve overlooked some crucial step or I have simply gotten something wrong. Maybe both. * – David. - This reply was modified 7 years, 3 months ago by [Steven Stern (sterndata)](https://wordpress.org/support/users/sterndata/). * Moderator [Steven Stern (sterndata)](https://wordpress.org/support/users/sterndata/) * (@sterndata) * Volunteer Forum Moderator * [7 years, 3 months ago](https://wordpress.org/support/topic/variable-mismatch/#post-10994068) * You’re replacing the entire array. I think you should be adding to the array passed in. * Thread Starter [dapike](https://wordpress.org/support/users/dapike/) * (@dapike) * [7 years, 3 months ago](https://wordpress.org/support/topic/variable-mismatch/#post-10995046) * I’ve now added the following code to both the page with the in it, as well as to the page that does the processing when the user clicks on the submit button: * ``` function my_filter_function_name( $string ) { $string += ['form' => array ('class' => True, 'action' => True, 'method' => True, 'style' => True)]; $string += ['input' => array ('class' => True, 'action' => True, 'method' => True, 'style' => True)]; $string += ['select' => array ('class' => True, 'action' => True, 'method' => True, 'style' => True)]; return $string; } add_filter( 'pre_kses', 'my_filter_function_name' ); ``` * However, the “A variable mismatch has been detected.” error message still arises when the user clicks on the submit button. - This reply was modified 7 years, 3 months ago by [Steven Stern (sterndata)](https://wordpress.org/support/users/sterndata/). * Thread Starter [dapike](https://wordpress.org/support/users/dapike/) * (@dapike) * [7 years, 3 months ago](https://wordpress.org/support/topic/variable-mismatch/#post-11000741) * I’m still struggling to try to restore the functionality that the WordPress upgrade broke. Something that I’m wondering… since the form that is coded into the html of the page in question does indeed get shown to users, along with the data entry fields and a button that can be pressed (and which ought to take the user to another page that does the processing), then this would seem to imply that tags such as “form”, “input” and “select” are not being automatically removed from the page’s html, and as such it seems that using a filter to avoid having them removed is not the correct course of action to be taking. * So unless my logic is flawed, then I think I’m back to asking my original question… how can I tell if there truly is a variable mismatch (as is being reported by the error message)? I note that the URL that is normally displayed after the user clicks the submit button and is taken to the secondary page for processing is actually the same URL as the original page (i.e., the original “www.mysite. org/?page_id=1234” URL remains on display) even though the new page actually has its own distinct page_id. Might that be the source of the reported variable mismatch? If so, how can I tell? And more critically, what can I do about it? * Thanks, * – David. * Moderator [Steven Stern (sterndata)](https://wordpress.org/support/users/sterndata/) * (@sterndata) * Volunteer Forum Moderator * [7 years, 3 months ago](https://wordpress.org/support/topic/variable-mismatch/#post-11001006) * According to what I see in trac, the problem introduced in 5.0.1 will be fixed in 5.0.3. * Thread Starter [dapike](https://wordpress.org/support/users/dapike/) * (@dapike) * [7 years, 3 months ago](https://wordpress.org/support/topic/variable-mismatch/#post-11003554) * Okay, I’ll wait for 5.0.3 to come out. * Thanks, * – David. * Thread Starter [dapike](https://wordpress.org/support/users/dapike/) * (@dapike) * [7 years, 2 months ago](https://wordpress.org/support/topic/variable-mismatch/#post-11081347) * WordPress 5.0.3 has been released, and I’ve upgraded my site to 5.0.3. * However, the “A variable mismatch has been detected.” error message persists. * What can I do? * [ComicNeue](https://wordpress.org/support/users/comicneue/) * (@comicneue) * [7 years, 2 months ago](https://wordpress.org/support/topic/variable-mismatch/#post-11091656) * I’ve been having this issue too. I just want to use `
` on a page and it’s impossible to use. I’ve tried adding the filter as described above and nothing. * Can someone please just outline how to make in page/post forms work? * Thread Starter [dapike](https://wordpress.org/support/users/dapike/) * (@dapike) * [7 years, 2 months ago](https://wordpress.org/support/topic/variable-mismatch/#post-11150112) * Can somebody who is “in the know” please say either when WordPress will fix this bug, or otherwise offer a reasonably clear description for how to work around it? * Thanks. Viewing 15 replies - 1 through 15 (of 18 total) 1 [2](https://wordpress.org/support/topic/variable-mismatch/page/2/?output_format=md) [→](https://wordpress.org/support/topic/variable-mismatch/page/2/?output_format=md) The topic ‘variable mismatch’ is closed to new replies. * In: [Fixing WordPress](https://wordpress.org/support/forum/how-to-and-troubleshooting/) * 18 replies * 5 participants * Last reply from: [Steven Stern (sterndata)](https://wordpress.org/support/users/sterndata/) * Last activity: [7 years, 1 month ago](https://wordpress.org/support/topic/variable-mismatch/page/2/#post-11267122) * Status: not resolved ## Topics ### Topics with no replies ### Non-support topics ### Resolved topics ### Unresolved topics ### All topics