different excerpt length on wordpress - php

Question

I want to register a custom length of excerpt on my wordpress plugin. If I add my custom excerpt length on my plugin and if user's theme have another custom excerpt length registered, will they make conflict? I noticed that fucntion name will be different but the filter's tag will be same('excerpt_length').
So, please let me clear about that.
Here is my excerpt length's code.
function custom_excerpt_length( $length ) {
return 40;
}
add_filter( 'excerpt_length', 'custom_excerpt_length');
Thanks.

Answer 1

I use this for a highly customized excerpt output (modified from Aaron Russell's code). It won't conflict with anything else you have. You can remove text values at will. It basically removes any filters for the excerpt output and overrides them.
// better excerpt output
function improved_trim_excerpt($text) {
global $post;
if ( '' == $text ) {
$text = get_the_content('');
$text = apply_filters('the_content', $text);
$text = str_replace('\]\]\>', ']]>', $text);
$text = preg_replace('#<script[^>]*?>.*?</script>#si', '', $text);
$text = strip_tags($text, '<p>');
$excerpt_length = 40;
$words = explode(' ', $text, $excerpt_length + 1);
if (count($words)> $excerpt_length) {
array_pop($words);
array_push($words, '... [<a href="' . get_permalink(). '" >Read More</a>]');
$text = implode(' ', $words);
}
}
return $text;
}
remove_filter('get_the_excerpt', 'wp_trim_excerpt');
add_filter('get_the_excerpt', 'improved_trim_excerpt');

Answer 2

If you use a function called custom_excerpt_length() and so does the theme, then you could have a conflict on the function name, but not the call to add_filter(). To mitigate the former you can either use an uncomment prefix (myplugin_custom_excerpt_length() for example) or better yet use a class to protect the namespace like $myplugin->custom_excerpt_length().
Adding multiple callbacks to actions/filters in WordPress won't cause a conflict, per se. If there are multiple actions/filters they are run in the order of their priority, which is the third argument to these functions. To give your filter hook a better chance of running last and thus be the value is used, set it to a high priority such as 999 - or at least higher than the function hooked to the filter you want to override, or lower than the default of 10 if you only want to set it if something else does. You can use this same class to add other actions/filters as well.
if ( ! class_exists( 'MyPlugin' ) ):
class MyPlugin(){
private $priority = 999;
private $excerpt_length = 40;
function __construct(){
// Use an array to pass $this and the function to add_filter()
add_filter( 'excerpt_length', array( $this, 'custom_excerpt_length' ) , $this->priority );
}
// The function name won't conflict since it is in the context of $this->excerpt_length()
function custom_excerpt_length( $length ){
return $this->excerpt_length;
}
}
new MyPlugin();
endif; // class_exists()