PHP str_replace with the contents of a file -

i'm wanting create short codes wordpress uses. when user puts [related] post, show content inside include "includes/related_article_inline.php" instead of [related]. i've tried far is:

$searchstring = '[related]'; $replacementstring = '<?php echo include "includes/related_article_inline.php"; ?>'; echo str_replace( $searchstring ,$replacementstring ,$post_content ); 

but, isn't quite working properly. know how can replace [related] contents of includes/related_article_inline.php?

str_replace doesn't include file, simple string-replacement. browser show

include "includes/related_article_inline.php";

somewhere, @ position added [replace].

two possible solutions.

1) if know on forehand [replace] in post-content: include before str_replace, store output string (using output-buffering), , actual replacement.

ob_start(); // start output buffering include "includes/related_article_inline.php"; $replacementstring = ob_get_clean(); // store output in variable, , stop output-buffering echo str_replace($searchstring, $replacementstring, $post_content); 

2) if don't know on forehand [replace] in post-content, don't want include it. use preg_replace_callback file included if necessary.

$replacementfunction = function() {     ob_start(); // start output buffering     include "includes/related_article_inline.php";     return ob_get_clean(); // return output, , stop output-buffering }; $searchregex = '/\[replace\]/'; // have rewrite search-string regular expression echo preg_replace_callback($searchregex, $replacementfunction, $post_content);