Using preg_replace to filter custom textarea

Question

I am developing a custom post type, which, among others includes the possibility of sending an email from within the post editor. The email body textarea is populated through a custom settings page and saved into a post_meta array which also includes the email and subject. Until here all fine.

The standard email content from the settings page includes %%PROPOSAL_LINK%% and %%PROPOSAL_LINK_URL%% which are supposed to be filtered out and replaced with a html link and a normal link to the permalink of the post where the email has originated from.

The following is the function as i have it right now:

function filter_email_text_for_post_link( $post ) {

// retrieve the 'proposal_email' post_meta (array)
$post_meta = get_post_meta( $post->ID, 'proposal_email', TRUE );
// retrieve email body 'proposal_email_text' from array
$email_content = $post_meta['proposal_email_text'];

// bail if email has no content
if( $email_content == '' ){ return; }

// patterns to look for in email body
$link_pattern = '%%PROPOSAL_LINK%%';
$url_pattern  = '%%PROPOSAL_LINK_URL%%';

// returns for each pattern
$proposal_link = '<a href="' . get_permalink( $post_id ) . '">here</a>';
$porposal_link_url = get_permalink( $post_id );

// match and replace with the above patterns
$email_content = str_replace( $link_pattern, $proposal_link, $email_content );
$email_content = str_replace( $url_pattern, $proposal_link_url, $email_content );

// update the post_meta
$post_meta['proposal_email_text'] = $email_content;
update_post_meta( $post->ID, 'proposal_email', $post_meta );

}

add_action( 'save_post', 'filter_email_text_for_post_link' );

for some reason, this just isn't working; at all, no errors, no nothing! Initially i tried invoking this function (slightly edited) in the function which saves the data on save_post but that wasn't working either.

Any suggestions?

Thanks in advance.

Answer 1

preg_replace expects it's regex to be surrounded by a character. Usually that's a slash, like this:

'/.*/'

When you do this:

preg_replace('%%PROPOSAL_LINK_URL%%', $some_text, $replacement);

preg_replace thinks the first two % are your surrounding characters, and fails because of an unrecognized modifier. This is easy to test:

$ php -a
Interactive shell

php > echo preg_replace('%%PROPOSAL_LINK_URL%%', '%%PROPOSAL_LINK_URL%%', 'here'), PHP_EOL;
PHP Warning:  preg_replace(): Unknown modifier 'P' in php shell code on line 1
PHP Stack trace:
PHP   1. {main}() php shell code:0
PHP   2. preg_replace() php shell code:1

Warning: preg_replace(): Unknown modifier 'P' in php shell code on line 1

Call Stack:
   28.9460     235264   1. {main}() php shell code:0
   28.9460     236016   2. preg_replace() php shell code:1


php > 

You have two options:

Change your patterns to something like this: /%%PROPOSAL_LINK_URL%%/ and /%%PROPOSAL_LINK%%/

$ php -a
Interactive shell

php > echo preg_replace('/%%PROPOSAL_LINK_URL%%/', '%%PROPOSAL_LINK_URL%%', 'here'), PHP_EOL;
here

Forget all about preg_replace because you don't need it. Use str_replace or str_ireplace instead.

<?php
str_replace('%%PROPOSAL_LINK_URL%%', $proposal_link_url, $email_content);
str_ireplace('%%PROPOSAL_LINK%%', $proposal_link, $email_content);

Be aware that str_replace and it's brethren are not safe for use on strings that contain multi-byte characters (eg. UTF-8) by default. You can change this.

NOTE: you've used $link_pattern twice in your code examples. I think you mean the second one to be $url_pattern.

EDIT: it appears there's not a mb_* replacement for str_replace or str_ireplace this comment on php.net sheds some light on the issue. str_replace should work on multibyte strings, providing the encoding of the needle and haystack are the same.

Answer 2

Your problem is a not-escaped regex. However you don't need preg_replace, just a str_replace

$email_content = str_replace( $link_pattern, $proposal_link, $email_content );
$email_content = str_replace( $link_pattern, $porposal_link_url, $email_content );

FYI, the right way for regex is, in this case:

$link_pattern = preg_quote('%%PROPOSAL_LINK%%');
$email_content = preg_replace( '/' . $link_pattern . '/', $proposal_link, $email_content);

Answer 3

The final, working function:

In comparison to my initial function ended up using str_replace in stead of preg_replace as the resulting code was shorter more concise and faster. Also added two arguments to the add_action call removing the need to use Global $post; furthermore removed notices in case where $post_meta['proposal_email_text'] has not been set (new post).

function filter_email_text_for_post_link( $post_id, $post ) {

// retrieve the 'proposal_email' post_meta (array)
$post_meta = get_post_meta( $post->ID, 'proposal_email', TRUE );
// retrieve email body 'proposal_email_text' from array
if( ! empty( $post_meta['proposal_email_text'] ) ){
    $email_content = $post_meta['proposal_email_text'];
} else {
    return; 
}

// bail if email has no content
if( $email_content == '' ){ return; }

// patterns to look for in email body
$link_pattern = '%%PROPOSAL_LINK%%';
$url_pattern  = '%%PROPOSAL_LINK_URL%%';

// returns for each pattern
$proposal_link = '<a href="' . get_permalink( $post_id ) . '">here</a>';
$proposal_link_url = get_permalink( $post_id );

// match and replace with the above patterns
$email_content = str_replace( $link_pattern, $proposal_link, $email_content );
$email_content = str_replace( $url_pattern, $proposal_link_url, $email_content );

// update the post_meta
$post_meta['proposal_email_text'] = $email_content;
update_post_meta( $post->ID, 'proposal_email', $post_meta );

}

add_action( 'save_post', 'filter_email_text_for_post_link', 10, 2 );