Title: Preg_replace not working Last modified: September 1, 2016 --- # Preg_replace not working * [diondkb](https://wordpress.org/support/users/diondkb/) * (@diondkb) * [9 years, 9 months ago](https://wordpress.org/support/topic/preg_replace-not-working/) * Hi, * Is there any reason why preg_replace should yield different results if run on an online test tool like [http://regexr.com/](http://regexr.com/) as opposed to running it in the wordpress context. * When this the following is run in the wordpress context, it finds a match and does the replacement, but not when run on two online regex tools. * The syntax is * ``` return preg_replace('/\.mp3(?!\?name)(?!"])/', '.mp3?name=[current_user]', $content ); ``` * The string to search is: ‘[html5_audio src=”[https://s3.amazonaws.com/sfs-premium/collection/Rider+Aids/Seat+Aids+and+Feel/Learning+How+to+Stop+Driving+with+Your+Seat/686-Learning-to-Stop-Driving-with-Your-Seat.mp3″%5D’](https://s3.amazonaws.com/sfs-premium/collection/Rider+Aids/Seat+Aids+and+Feel/Learning+How+to+Stop+Driving+with+Your+Seat/686-Learning-to-Stop-Driving-with-Your-Seat.mp3″%5D’); * **Running the expression on the online tool, yields:** [html5_audio src=”[https://s3.amazonaws.com/sfs-premium/collection/Rider+Aids/Seat+Aids+and+Feel/Learning+How+to+Stop+Driving+with+Your+Seat/686-Learning-to-Stop-Driving-with-Your-Seat.mp3″%5D](https://s3.amazonaws.com/sfs-premium/collection/Rider+Aids/Seat+Aids+and+Feel/Learning+How+to+Stop+Driving+with+Your+Seat/686-Learning-to-Stop-Driving-with-Your-Seat.mp3″%5D) * **while run in the wordpress environment yields:** [html5_audio src=”[https://s3.amazonaws.com/sfs-premium/collection/Rider+Aids/Seat+Aids+and+Feel/Learning+How+to+Stop+Driving+with+Your+Seat/686-Learning-to-Stop-Driving-with-Your-Seat.mp3?name=%5Bcurrent_user%5D”%5D](https://s3.amazonaws.com/sfs-premium/collection/Rider+Aids/Seat+Aids+and+Feel/Learning+How+to+Stop+Driving+with+Your+Seat/686-Learning-to-Stop-Driving-with-Your-Seat.mp3?name=%5Bcurrent_user%5D”%5D) * Does wordpress add chars causing the opposite results? * Any help will be appreciated. * Dion Viewing 12 replies - 1 through 12 (of 12 total) * [RossMitchell](https://wordpress.org/support/users/rossmitchell/) * (@rossmitchell) * [9 years, 9 months ago](https://wordpress.org/support/topic/preg_replace-not-working/#post-7618946) * You are putting a leading and trailing “/” on your search string, these are part of the syntax for many editor commands, but here PHP just wants the search strings. * Thread Starter [diondkb](https://wordpress.org/support/users/diondkb/) * (@diondkb) * [9 years, 9 months ago](https://wordpress.org/support/topic/preg_replace-not-working/#post-7618949) * Hi. Not according to this example… * ``` ``` * …found here [http://php.net/manual/en/function.preg-replace.php](http://php.net/manual/en/function.preg-replace.php) * [RossMitchell](https://wordpress.org/support/users/rossmitchell/) * (@rossmitchell) * [9 years, 9 months ago](https://wordpress.org/support/topic/preg_replace-not-working/#post-7618953) * That example does not work for me ? Only has “/” at start. Please try it without the “/”. * Thread Starter [diondkb](https://wordpress.org/support/users/diondkb/) * (@diondkb) * [9 years, 9 months ago](https://wordpress.org/support/topic/preg_replace-not-working/#post-7618954) * Here is the code(placed in a shortcode) * ``` function add_user_to_mp3( $content ) { return preg_replace('\.mp3(?!\?name)(?!"])', '.mp3?name=[current_user]', $content ); } add_filter( 'content_save_pre' , 'add_user_to_mp3' , 10, 1); ``` * When I refresh the web page, I get the following error – Warning: preg_replace(): Delimiter must not be alphanumeric or backslash in * Thread Starter [diondkb](https://wordpress.org/support/users/diondkb/) * (@diondkb) * [9 years, 9 months ago](https://wordpress.org/support/topic/preg_replace-not-working/#post-7618955) * I stuck the same piece of code into one of my web pages and got the correct output- * ``` ``` * preg_replace does not seem to work correctly in the context of a shortcode? * Moderator [bcworkz](https://wordpress.org/support/users/bcworkz/) * (@bcworkz) * [9 years, 9 months ago](https://wordpress.org/support/topic/preg_replace-not-working/#post-7618966) * But your web page code is not the same as the shortcode handler code. In the webpage version you’ve properly used ‘/’ as regexp delimiters, but not in the shortcode version. `preg_replace()` works the same in either context as long as your regexp is properly formatted! * BTW, you can use any character as a delimiter as long as it does not occur in the regexp proper. Or if it does it must be escaped. * Thread Starter [diondkb](https://wordpress.org/support/users/diondkb/) * (@diondkb) * [9 years, 9 months ago](https://wordpress.org/support/topic/preg_replace-not-working/#post-7618987) * Thanks for your patience. I changed the shortcode as requested with no change- * ``` function add_user_to_mp3( $content ) { return preg_replace('/\.mp3(?!\?name)(?!"])/', '.mp3?name=[current_user]', $content ); } add_filter( 'content_save_pre' , 'add_user_to_mp3' , 10, 1); After editing the page containing the shortcode in the wordpress editor, and adding this code and then saving, the code changes from this: ``` * * [html5_audio src=”[https://s3.amazonaws.com/sfs-premium/collection/Rider+Aids/Seat+Aids+and+Feel/Learning+How+to+Stop+Driving+with+Your+Seat/686-Learning-to-Stop-Driving-with-Your-Seat.mp3″%5D](https://s3.amazonaws.com/sfs-premium/collection/Rider+Aids/Seat+Aids+and+Feel/Learning+How+to+Stop+Driving+with+Your+Seat/686-Learning-to-Stop-Driving-with-Your-Seat.mp3″%5D) * ``` to this: ``` * * [html5_audio src=”[https://s3.amazonaws.com/sfs-premium/collection/Rider+Aids/Seat+Aids+and+Feel/Learning+How+to+Stop+Driving+with+Your+Seat/686-Learning-to-Stop-Driving-with-Your-Seat.mp3?name=%5Bcurrent_user%5D”%5D](https://s3.amazonaws.com/sfs-premium/collection/Rider+Aids/Seat+Aids+and+Feel/Learning+How+to+Stop+Driving+with+Your+Seat/686-Learning-to-Stop-Driving-with-Your-Seat.mp3?name=%5Bcurrent_user%5D”%5D) ` I copied the exact same preg_replace pattern(‘/\.mp3(?!\?name)(?!”])/’) from the shortcode function(which at this point does not seem to work) and pasted it in the web page mentioned previously and did a hard refresh and the pattern behaves as expected ie not doing the replacement(‘.mp3?name=[current_user]’)? * Any ideas I can try. Thanks * Thread Starter [diondkb](https://wordpress.org/support/users/diondkb/) * (@diondkb) * [9 years, 9 months ago](https://wordpress.org/support/topic/preg_replace-not-working/#post-7618988) * sorry. got the tags a little mixed up. * [Maria Daniel Deepak](https://wordpress.org/support/users/mariadanieldeepak/) * (@mariadanieldeepak) * [9 years, 9 months ago](https://wordpress.org/support/topic/preg_replace-not-working/#post-7618989) * [@diondkb](https://wordpress.org/support/users/diondkb/), * In addition to [@bcworkz](https://wordpress.org/support/users/bcworkz/) answer, PHP uses [PCRE functions](http://www.pcre.org/) and it requires you to use [delimiters](http://php.net/manual/en/regexp.reference.delimiters.php) when you’re finding patterns using regex. * Some of the commonly used delimiters are * ``` /foo bar/ #^[^0-9]$# +php+ %[a-zA-Z0-9_-]% ``` * [Maria Daniel Deepak](https://wordpress.org/support/users/mariadanieldeepak/) * (@mariadanieldeepak) * [9 years, 9 months ago](https://wordpress.org/support/topic/preg_replace-not-working/#post-7618991) * [@diondkb](https://wordpress.org/support/users/diondkb/), * Could you tell us in simple terms what your end result should look like? (i.e. Your string and what you want achieve with it?) * Thread Starter [diondkb](https://wordpress.org/support/users/diondkb/) * (@diondkb) * [9 years, 9 months ago](https://wordpress.org/support/topic/preg_replace-not-working/#post-7619026) * Hi, * If the line of text ends in ‘.mp3″]’, then don’t do the replacement. So, * ``` [html5_audio src="https://s3.amazonaws.com/sfs-premium/collection/Rider+Aids/Seat+Aids+and+Feel/Learning+How+to+Stop+Driving+with+Your+Seat/686-Learning-to-Stop-Driving-with-Your-Seat.mp3"] ``` * … would not change, while * ```