Slow functions cause by array_merge in loops - php

Question

I have two functions which appear to be slowing down PHP, and I believe its to do with the use of array_merge in the loops, only I am struggling to figure out how I can get around not doing so.
function fuseOzone($field) {
global $ozone;
if(isset($ozone['all'])) {
foreach($ozone['all'] as $priority => $functions) {
if(isset($ozone[$field][$priority])) {
$ozone[$field][$priority] = array_merge($ozone['all'][$priority], $ozone[$field][$priority]);
} else {
$ozone[$field][$priority] = array_merge($ozone['all'][$priority], array());
$ozone[$field][$priority] = array_unique($ozone[$field][$priority]);
}
}
}
if(isset($ozone[$field])) {
ksort($ozone[$field]);
}
}
function applyOzone($field, $content) {
global $ozone;
fuseOzone($field);
$args = array_slice(func_get_args(), 2);
if(isset($ozone[$field])) {
foreach($ozone[$field] as $priority => $functions) {
if(!is_null($functions)) {
foreach($functions as $function) {
if(!function_exists($function['function'])) {
continue;
}
$all_args = array_merge(array($content), $args);
$function_name = $function['function'];
$accepted_args = $function['accepted_args'];
if($accepted_args === 1) {
$the_args = array($content);
} elseif($accepted_args > 1) {
$the_args = array_slice($all_args, 0, $accepted_args);
} elseif($accepted_args === 0) {
$the_args = null;
} else {
$the_args = $all_args;
}
$content = call_user_func_array($function_name, $the_args);
}
}
}
}
return $content;
}
These functions are part of a larger class which essentially operates much like Wordpress actions. I.e. I can hook into a portion of content with filtering or such.