Symfony\Component\Process\ExecutableFinder::find PHP Method

    public function find($name, $default = null, array $extraDirs = array())
    {
        if (ini_get('open_basedir')) {
            $searchPath = explode(PATH_SEPARATOR, getenv('open_basedir'));
            $dirs = array();
            foreach ($searchPath as $path) {
                if (is_dir($path)) {
                    $dirs[] = $path;
                } else {
                    $file = str_replace(dirname($path), '', $path);
                    if ($file == $name && is_executable($path)) {
                        return $path;
                    }
                }
            }
        } else {
            $dirs = array_merge(
                explode(PATH_SEPARATOR, getenv('PATH') ?: getenv('Path')),
                $extraDirs
            );
        }

        $suffixes = array('');
        if (defined('PHP_WINDOWS_VERSION_BUILD')) {
            $pathExt = getenv('PATHEXT');
            $suffixes = $pathExt ? explode(PATH_SEPARATOR, $pathExt) : $this->suffixes;
        }
        foreach ($suffixes as $suffix) {
            foreach ($dirs as $dir) {
                if (is_file($file = $dir.DIRECTORY_SEPARATOR.$name.$suffix) && (self::$isWindows || is_executable($file))) {
                    return $file;
                }
            }
        }

        return $default;
    }

 /**
  * Generates the configuration tree builder.
  *
  * @return \Symfony\Component\Config\Definition\Builder\TreeBuilder The tree builder
  */
 public function getConfigTreeBuilder()
 {
     $builder = new TreeBuilder();
     $finder = new ExecutableFinder();
     $builder->root('assetic')->children()->booleanNode('debug')->defaultValue($this->debug)->end()->booleanNode('use_controller')->defaultValue($this->debug)->end()->scalarNode('read_from')->defaultValue('%kernel.root_dir%/../web')->end()->scalarNode('write_to')->defaultValue('%assetic.read_from%')->end()->scalarNode('java')->defaultValue($finder->find('java', '/usr/bin/java'))->end()->scalarNode('node')->defaultValue($finder->find('node', '/usr/bin/node'))->end()->scalarNode('sass')->defaultValue($finder->find('sass', '/usr/bin/sass'))->end()->end()->fixXmlConfig('bundle')->children()->arrayNode('bundles')->defaultValue($this->bundles)->requiresAtLeastOneElement()->prototype('scalar')->validate()->ifNotInArray($this->bundles)->thenInvalid('%s is not a valid bundle.')->end()->end()->end()->end()->fixXmlConfig('asset')->children()->arrayNode('assets')->addDefaultsIfNotSet()->requiresAtLeastOneElement()->useAttributeAsKey('name')->prototype('array')->beforeNormalization()->ifTrue(function ($v) {
         return !is_array($v);
     })->then(function ($v) {
         return array('inputs' => array($v));
     })->end()->beforeNormalization()->always()->then(function ($v) {
         // cast scalars as array
         foreach (array('input', 'inputs', 'filter', 'filters') as $key) {
             if (isset($v[$key]) && !is_array($v[$key])) {
                 $v[$key] = array($v[$key]);
             }
         }
         // organize arbitrary options
         foreach ($v as $key => $value) {
             if (!in_array($key, array('input', 'inputs', 'filter', 'filters', 'option', 'options'))) {
                 $v['options'][$key] = $value;
                 unset($v[$key]);
             }
         }
         return $v;
     })->end()->fixXmlConfig('input')->fixXmlConfig('filter')->children()->arrayNode('inputs')->prototype('scalar')->end()->end()->arrayNode('filters')->prototype('scalar')->end()->end()->arrayNode('options')->useAttributeAsKey('name')->prototype('variable')->end()->end()->end()->end()->end()->end()->fixXmlConfig('filter')->children()->arrayNode('filters')->addDefaultsIfNotSet()->requiresAtLeastOneElement()->useAttributeAsKey('name')->prototype('variable')->treatNullLike(array())->validate()->ifTrue(function ($v) {
         return !is_array($v);
     })->thenInvalid('The assetic.filters config %s must be either null or an array.')->end()->end()->end()->end()->children()->arrayNode('twig')->addDefaultsIfNotSet()->defaultValue(array())->fixXmlConfig('function')->children()->arrayNode('functions')->addDefaultsIfNotSet()->defaultValue(array())->useAttributeAsKey('name')->prototype('variable')->treatNullLike(array())->validate()->ifTrue(function ($v) {
         return !is_array($v);
     })->thenInvalid('The assetic.twig.functions config %s must be either null or an array.')->end()->end()->end()->end()->end()->end();
     return $builder;
 }