Pure PHP array_diff_assoc_recursive function

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For my application, I was using array_diff_assoc, when I noticed it was returning the wrong value. I was using multidimensional arrays, therefore I needed a array_diff_assoc_recursive method.

I Googled around and found a few, but they all only took 2 parameters. The official array_diff_assoc can take an infinite number of params. I wanted mine to, so I wrote my own array_diff_assoc_recursive function.

class Tools{
     * Recursive version of array_diff_assoc
     * Returns everything from $a that is not in $b or the other arguments
     * @param $a The array to compare from
     * @param $b An array to compare against
     * @param ... More arrays to compare against
     * @return An array with everything from $a that not in $b or the others
    public static function array_diff_assoc_recursive($a, $b){
        // Get all of the "compare against" arrays
        $b = array_slice(func_get_args(), 1);
        // Initial return value
        $ret = array();

        // Loop over the "to" array and compare with the others
        foreach($a as $key=>$val){
            // We should compare type first
            $aType = gettype($val);
            // If it's an array, we recurse, otherwise we just compare with "==="
            $args = $aType === 'array' ? array($val) : true;

            // Let's see what we have to compare to
            foreach($b as $x){
                // If the key doesn't exist or the type is different,
                // then it's different, and our work here is done
                if(!array_key_exists($key, $x) || $aType !== gettype($x[$key])){
                    $ret[$key] = $val;
                    continue 2;

                // If we are working with arrays, then we recurse
                if($aType === 'array'){
                    $args[] = $x[$key];
                // Otherwise we just compare
                    $args = $args && $val === $x[$key];

            // This is where we call ourselves with all of the arrays we got passed
            if($aType === 'array'){
                $comp = call_user_func_array(array(get_called_class(), 'array_diff_assoc_recursive'), $args);
                // An empty array means we are equal :-)
                if(count($comp) > 0){
                    $ret[$key] = $comp;
            // If the values don't match, then we found a difference
                $ret[$key] = $val;
        return $ret;

I was wondering what you thought of my attempt. It seems to work ok for my application, and in the few tests I tried with it.

DEMO: http://ideone.com/5GZ8Tn


The logic looks good but I would like to suggest a few tips to enhance readability and maintainability of your code.

First off: name your variables accordingly $a doesn’t say anything to any random person when reading the code. He will have to scroll up and down figuring out what is what.

Second: Split your function into multiple methods. This will enhance readability and will keep an overview of your code. Now you have one very large method which will take a random person at least half an hour to figure out what it all does exactly.

Third: Try to avoid things like continue 2;, break; and more. They don’t mean anything when you read code and can be avoided in most cases.

Fourth: Comments rot very quickly! Try and make sure that your methods are selfexplanatory so that you dont need to put comments.

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