RegexHelpers.php

class NamespaceSeparator
{
    public function __toString()
    {
        return '\x5c';
    }
}

class NamedGroup
{
    private $name, $regex;
    
    public function __construct($name, $regex)
    {
        $this->name = $name;
        $this->regex = $regex;
    }

    public function __toString()
    {
        return
            (string) 
            new Group("?P<{$this->name}>{$this->regex}")
        ;
    }
}

class ValidClassName
{
    public function __toString()
    {
        return 
            (string)
            new ZeroOrMoreOf(
                new CharacterClass('a-zA-Z_\x7f-\xff') 
              . new CharacterClass('a-zA-Z0-9_\x7f-\xff')
            )
        ;
    }
}

class ValidNamespace
{
    public function __toString()
    {
        return
              new ValidClassName
            . new Optional(
                    new ZeroOrMoreOf(
                        new Group(new NamespaceSeparator . new ValidClassName) 
                    ) 
              )
        ;
    }
}


class Optional
{
    private $regex;
    
    public function __construct($regex)
    {
        $this->regex = $regex;
    }

    public function __toString()
    {
        return (string) new Group("?:{$this->regex}") . '?';
    }
}

class Group
{
    private $regex;
    
    public function __construct($regex)
    {
        $this->regex = $regex;
    }

    public function __toString()
    {
        return "({$this->regex})";
    }
}

class CharacterClass
{
    private $characters;
    
    public function __construct($characters)
    {
        $this->characters = $characters;
    }

    public function __toString()
    {
        return 
               '['
             . $this->characters
             . ']'
        ;
    }
}

class ZeroOrMoreOf
{
    private $regex;
    
    public function __construct($regex)
    {
        $this->regex = $regex;
    }

    public function __toString()
    {
        return "{$this->regex}*";
    }
}

class OneOrMoreOf
{
    private $regex;
    
    public function __construct($regex)
    {
        $this->regex = $regex;
    }

    public function __toString()
    {
        return "{$this->regex}+";
    }
}

class Space
{
    public function __toString()
    {
        return '\s';
    }
}

class SpacesAround
{
    private $regex;
    
    public function __construct($regex)
    {
        $this->regex = $regex;
    }

    public function __toString()
    {
        return 
              new OneOrMoreOf(new Space)
            . $this->regex
            . new OneOrMoreOf(new Space)
        ;
    }
}

class WordBoundary
{
    public function __toString()
    {
        return '\b';
    }
}

class WordBoundaryAround
{
    private $regex;
    
    public function __construct($regex)
    {
        $this->regex = $regex;
    }

    public function __toString()
    {
        return 
               new WordBoundary
             . $this->regex
             . new WordBoundary
        ;
    }
}

class OptionalSpacesAround
{
    private $regex;
    
    public function __construct($regex)
    {
        $this->regex = $regex;
    }

    public function __toString()
    {
        return 
              new OneOrMoreOf(new Optional(new Space))
            . $this->regex
            . new OneOrMoreOf(new Optional(new Space))
        ;
    }
}

class Alteration
{
    private $options;
    
    public function __construct(array $options)
    {
        $this->options = $options;
    }

    public function __toString()
    {
        return implode('|', $this->options);
    }
}

class CaseInsensitiveMatch
{
    public function __toString()
    {
        return 'i';
    }
}

class MultiLineMatch
{
    public function __toString()
    {
        return 'm';
    }
}