Function to inspect WordPress filters/actions that match a regular expression

gistfile1.php

<?php

//hook into the 'shutdown' action and debug some filters... but not on the admin this time
if (! is_admin() )
    add_action('shutdown', 'use_debug_filters',10);
    
function use_debug_filters(){
    
    echo "<h3>Output hooks and filters that contain the string 'init'</h3>";
    debug_filter("/init/i");
    
    echo "<h3>Output hooks and filters that contain the string 'before'</h3>";
    debug_filter("/before/i");
    
    echo "<h3>Output hooks and filters that start with 'wp'</h3>";
    debug_filter("/^wp/i");
    
}
    
/**
 * Loop through $wp_filter array and output any actions/filters that match the regular expression passed in.
 */
function debug_filter($regex_filter_action_to_match = "//"){
     global $wp_filter;
     $hook=$wp_filter;
     ksort($hook);
     
     
     echo "<pre style='background-color:white;'>";
     foreach($hook as $tag => $priority){
         
         //check for a regex match of hook name
         if ( !preg_match($regex_filter_action_to_match, $tag) ) continue;

         
      echo "<br /><strong>$tag</strong><br />";
      ksort($priority);
      foreach($priority as $priority => $function){
      echo " $priority \n";
          foreach($function as $name => $properties) {
     
        
              echo "\t$name  ";
              
                if ( function_exists($name) ){
                    $func = new ReflectionFunction($name);
                    $filename = $func->getFileName();
                    $start_line = $func->getStartLine() - 1; // it's actually - 1, otherwise you wont get the function() block
                    $path_info = pathinfo($filename);
                        echo "<em style='font-size:90%;opacity:0.5;' title='{$filename}'> {$path_info[filename]}.{$path_info[extension]}: line {$start_line}</em>";
                }
              echo "<br />";
          }
      }
     }
     echo '</pre>';
     return;
}