Detect conflicting rewrites in a Magento installation

rewrites.php

<?php

function get_flag($value) {
    $value = strtolower($value);
    return $value === TRUE || ($value !== 'false' && !!$value);
}

$modules_dir = dir('app/etc/modules/');
$rewrites = array();
$conflicts = array();


while ($mod = $modules_dir->read()) {
    if (in_array($mod, array('.', '..'))) continue;
    try {
        $config = new SimpleXMLElement(file_get_contents('app/etc/modules/' . $mod));
    } catch (Exception $e) {
        continue;
    }
    $modules = reset($config->modules);

    foreach (get_object_vars($config->modules) as $name => $module) {
        if (isset($module->active) && get_flag($module->active)) {
            $pool = $module->codePool;
            $configFile = 'app/code/' . $pool . '/' . implode('/', explode('_', $name, 2)) . '/etc/config.xml';
            
            if (!file_exists($configFile)) {
                continue;
            }
            
            $mod_config = new SimpleXMLElement(file_get_contents($configFile));

            $types = array('models', 'blocks', 'helpers');
            
            foreach ($types as $type) {
                foreach($mod_config->xpath("//{$type}") as $type_node) {
                    foreach (get_object_vars($type_node) as $namespace => $data) {
                        foreach ($type_node->xpath($namespace . '//rewrite') as $rewrite) {
                            foreach (get_object_vars($rewrite) as $original => $new) {
                                if (empty($rewrites["{$type}/{$namespace}/{$original}"])) {
                                    $rewrites["{$type}/{$namespace}/{$original}"] = $new;
                                } else {
                                
                                    if (empty($conflicts["{$type}/{$namespace}/{$original}"])) {
                                        $conflicts["{$type}/{$namespace}/{$original}"] = array($rewrites["{$type}/{$namespace}/{$original}"]);
                                    }
                                    
                                    $conflicts["{$type}/{$namespace}/{$original}"][] = $new;
                                }
                                
                                echo str_pad("Rewrite ({$mod}):", 44) . "{$type}/{$namespace}/$original => {$new}\n";
                            }
                        }
                    }
                }
            }
        }
    }
}

require_once "app/Mage.php";

if (!empty($conflicts)) {
    echo "Conflicting rewrites:\n";
    foreach ($conflicts as $resource => $conflictingRewrites) {
    
        echo $resource . "\n";
        
        foreach ($conflictingRewrites as $r) {
            echo "\t* {$r}\n";
        }
        
        $resolved = TRUE;       
        $nConflicts = count($conflictingRewrites);
        for ($i = 0; $i < $nConflicts && $resolved == TRUE; $i++) {
            for ($j = 0; $j < $nConflicts - 1; $j++) {
                if (is_subclass_of($conflictingRewrites[$j + 1], $conflictingRewrites[$j])) {
                    $temp = $conflictingRewrites[$j + 1];
                    $conflictingRewrites[$j + 1] = $conflictingRewrites[$j];
                    $conflictingRewrites[$j] = $temp;
                } else {
                    // Verifico si el arbol de herencia esta cortado
                    if (!is_subclass_of($conflictingRewrites[$j], $conflictingRewrites[$j + 1])) {
                        $resolved = FALSE;
                        break;
                    }
                }
            }
        }
        
        if ($resolved) {
            echo "\t--- RESOLVED ---\n";
        }
    }
    
}