absolute-to-relative-urls.php

<?php
/*
Absolute-to-Relative URLs 0.3.4 <http://www.svachon.com/blog/absolute-to-relative-urls/>
A class for use in shortening URL links.
*/

class Absolute_to_Relative_URLs
{
	//protected static $_instance;
	
	protected $custom_ports;
	protected $site_port_is_default;
	protected $site_url;
	
	
	
	/*
		$custom_site_url :: should be a valid URL, with scheme and host
		$custom_ports    :: e.g., array('ssh'=>22)
	*/
	public function __construct($custom_site_url='', $custom_ports=array())
	{
		$this->custom_ports = $custom_ports;
		
		$this->get_site_url($custom_site_url);
		
		if ($this->site_url === false)
		{
			trigger_error('Invalid site URL');
		}
	}
	
	
	
	/*
		Initialize class for absolute_to_relative_url()
		Nice idea, BUT slower than using a global variable
	*/
	/*public static function instance()
	{
		if (self::$_instance === null)
		{
			self::$_instance = new Absolute_to_Relative_URLs();
		}
		
		return self::$_instance;
	}*/
	
	
	
	protected function build_url($url, $output_type)
	{
		$has_fragment = isset($url['fragment']);
		$has_resource = isset($url['resource']);
		$has_query    = isset($url['query']);
		
		if ( isset($url['scheme']) )
		{
			$first_half = $url['scheme'] . ':';
		}
		else
		{
			$first_half = '';
		}
		
		if ( isset($url['host']) )
		{
			$first_half .= '//';
			
			$user_or_pass = false;
			
			if ( isset($url['user']) )
			{
				$first_half .= $url['user'];
				
				$user_or_pass = true;
			}
			
			if ( isset($url['pass']) )
			{
				$first_half .= ':' . $url['pass'];
				
				$user_or_pass = true;
			}
			
			if ($user_or_pass)
			{
				$first_half .= '@';
			}
			
			$first_half .= $url['host'];
			
			if ( isset($url['port']) )
			{
				$first_half .= ':' . $url['port'];
			}
			
			$second_half = $url['path'];
		}
		else
		{
			if ($output_type===1 || $output_type===2)
			{
				$absolute_path = $url['path'];
				$relative_path = (isset($url['path_relative'])) ? $url['path_relative'] : false;
				
				if ($relative_path !== false)
				{
					if ($output_type === 2)
					{
						$second_half = (strlen($relative_path) <= strlen($absolute_path)) ? $relative_path : $absolute_path;
					}
					else
					{
						$second_half = $relative_path;
					}
				}
				else
				{
					$second_half = $absolute_path;
				}
			}
			else if ($output_type === 0)
			{
				$second_half = $url['path'];
			}
			
			if ($has_resource || $has_query || $has_fragment)
			{
				if ($second_half==='./' || ($second_half==='/' && $this->site_url['path']==='/'))
				{
					$second_half = '';
				}
			}
		}
		
		if ($has_resource)
		{
			$second_half .= $url['resource'];
		}
		
		if ($has_query)
		{
			$second_half .= '?'. $url['query'];
		}
		
		if ($has_fragment)
		{
			$second_half .= '#'. $url['fragment'];
		}
		
		return $first_half . $second_half;
	}
	
	
	
	protected function get_default_port($scheme)
	{
		switch ($scheme)
		{
			case 'http'		:	return 80;
			case 'https'	:	return 443;
			case 'ftp'		:	return 21;
		}
		
		foreach ($this->custom_ports as $port_name => $port)
		{
			$port_name = strtolower($port_name);
			
			if ($port_name === $scheme)
			{
				return $port;
			}
		}
		
		// No listed match found
		return -1;
	}
	
	
	
	protected function get_site_url($custom_site_url)
	{
		if ($custom_site_url === '')
		{
			$this->custom_site_url = true;
			
			$url = ( !isset($_SERVER['HTTPS']) )   ?   'http://' : 'https://';
			
			if ( isset($_SERVER['PHP_AUTH_USER']) )
			{
				$url .= $_SERVER['PHP_AUTH_USER'] .':'. $_SERVER['PHP_AUTH_PW'] .'@';
			}
			
			$url .= $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'];
		}
		else
		{
			$url = $custom_site_url;
		}
		
		$url = $this->parse_url($url, true);
		
		if ($url !== false)
		{
			if ( isset($url['port']) )
			{
				$this->site_port_is_default = ($url['port'] === $this->get_default_port($url['scheme']));
			}
			else
			{
				$url['port'] = $this->get_default_port($url['scheme']);
				
				$this->site_port_is_default = true;
			}
			
			$url['host_stripped'] = $this->remove_www($url['host']);
		}
		
		$this->site_url = $url;
	}
	
	
	
	/*
		Return an path string.
	*/
	protected function implode_path($path, $absolute_output)
	{
		if (!empty($path))
		{
			$path = implode('/', $path) .'/';
			
			if ($absolute_output)
			{
				$path = '/'.$path;
			}
		}
		else
		{
			$path = (!$absolute_output) ? './' : '/';
		}
		
		return $path;
	}
	
	
	
	/*
		Return an absolute path.
	*/
	protected function parse_path($path)
	{
		if ($path !== '/')
		{
			$path = explode('/', $path);
			$absolute_path = array();
			
			$first_dir = $path[0];
			
			// Check if not absolute: '/dir/' becomes array('','dir','')
			if ($first_dir !== '')
			{
				if ($first_dir==='.' || $first_dir==='..')
				{
					$path = array_merge($this->site_url['path_array'], $path);
				}
			}
			
			foreach ($path as $dir)
			{
				if ($dir !== '')
				{
					if ($dir !== '..')
					{
						if ($dir !== '.')
						{
							array_push($absolute_path, $dir);
						}
					}
					else
					{
						$parent_index = count($absolute_path) - 1;
						
						if ($parent_index >= 0)
						{
							unset( $absolute_path[$parent_index] );
							$absolute_path = array_values($absolute_path);
						}
					}
				}
			}
			
			return $absolute_path;
		}
		else
		{
			// Faster to skip the above block and just create an array
			return array();
		}
	}
	
	
	
	/*
		Return the components of a URL.
	*/
	protected function parse_url($url, $init=false)
	{
		if ( stripos($url,'data:')===0 || stripos($url,'javascript:')===0 )
		{
			// Nothing can be done with data/javascript URIs
			return false;
		}
		else if (strpos($url, '//') === 0)
		{
			// Cannot parse scheme-relative URLs with parse_url
			$url = $this->site_url['scheme'] . ':' . $url;
		}
		
		// With PHP versions earlier than 5.3.3, an E_WARNING is emitted when URL parsing fails
		// REMOVE when WordPress enforces a higher version as it will increase performance
		$url = @parse_url($url);
		
		if ($url !== false)
		{
			if ($init)
			{
				// Checks for host to catch "host:80"
				if ( !isset($url['scheme']) || !isset($url['host']) )
				{
					// Invalid site url
					return false;
				}
			}
			
			if ( isset($url['path']) )
			{
				$path = str_replace(' ', '%20', $url['path']);
				
				$last_slash = strrpos($path, '/');
				
				if ($last_slash !== false)
				{
					$last_slash++;
					
					if ($last_slash < strlen($path))
					{
						// Isolate resource from path
						$url['resource'] = substr($path, $last_slash);
						
						$path = substr($path, 0, $last_slash);
					}
					
					$url['path_array'] = $this->parse_path($path);
					$url['path'] = $this->implode_path($url['path_array'], true);
				}
				else
				{
					// No slashes found
					$url['resource'] = $path;
					
					$url['path'] = $this->site_url['path'];
					$url['path_array'] = $this->site_url['path_array'];
				}
			}
			else if ( isset($url['host']) )
			{
				$url['path'] = '/';
				$url['path_array'] = array();
			}
			else
			{
				$url['path'] = $this->site_url['path'];
				$url['path_array'] = $this->site_url['path_array'];
			}
		}
		
		return $url;
	}
	
	
	
	/*
		Return a path relative to the site path.
	*/
	protected function relate_path($absolute_path)
	{
		$relative_path = array();
		$site_path = $this->site_url['path_array'];
		
		// At this point, it's related to the host
		$related = true;
		$parent_index = -1;
		
		// Find parents
		foreach ($site_path as $i => $dir)
		{
			if ($related)
			{
				$absolute_dir = (isset($absolute_path[$i])) ? $absolute_path[$i] : null;
				
				if ($dir !== $absolute_dir)
				{
					$related = false;
				}
				else
				{
					$parent_index = $i;
				}
			}
			
			if (!$related)
			{
				// Up one level
				array_push($relative_path, '..');
			}
		}
		
		// Form path
		foreach ($absolute_path as $i => $dir)
		{
			if ($i > $parent_index)
			{
				array_push($relative_path, $dir);
			}
		}
		
		return $relative_path;
	}
	
	
	
	/*
		Return a URL relative to the site URL.
		
		$ignore_www  :: optionally, ignore "www" subdomain
		$output_type :: optionally, return either a:
				0: root-relative URL (/child-of-root/etc/)
				1: path-relative URL (../child-of-parent/etc/)
				2: shortest possible URL (root- or path-relative)
	*/
	public function relate_url($url, $ignore_www=false, $output_type=2)
	{
		if ($this->site_url !== false)
		{
			if ($url==='' || $url==='.' || $url==='./')
			{
				if ($this->site_url['path'] !== '/')
				{
					if ($output_type===1 || $output_type===2)
					{
						return './';
					}
					else if ($output_type === 0)
					{
						return $this->site_url['path'];
					}
				}
				else
				{
					return '/';
				}
			}
			else if ($url === '/')
			{
				return '/';
			}
			else if ($url === '#')
			{
				return '#';
			}
			
			$original_url = $url;
			
			$url = $this->parse_url($url);
			
			if ($url === false)
			{
				// Unusable format
				return $original_url;
			}
		}
		else
		{
			// Invalid site url
			return $url;
		}
		
		$related = false;
		
		if ( isset($url['scheme']) )
		{
			$scheme = $url['scheme'];
			
			if ($scheme === $this->site_url['scheme'])
			{
				unset($url['scheme']);
				
				if ($ignore_www)
				{
					$url['host'] = $this->remove_www($url['host']);
					
					$site_host = $this->site_url['host_stripped'];
				}
				else
				{
					$site_host = $this->site_url['host'];
				}
				
				if ($url['host'] === $site_host)
				{
					$related = true;
					
					if ( isset($url['port']) )
					{
						if ($url['port'] === $this->site_url['port'])
						{
							unset($url['port']);
						}
						else
						{
							$related = false;
						}
					}
					else if (!$this->site_port_is_default)
					{
						$related = false;
					}
					
					if ( isset($url['user']) )
					{
						if (!isset($this->site_url['user']) || $url['user'] !== $this->site_url['user'])
						{
							$related = false;
						}
					}
					/*else if ( isset($this->site_url['user']) )
					{
						$related = false;
					}*/
					
					if ( isset($url['pass']) )
					{
						if (!isset($this->site_url['pass']) || $url['pass'] !== $this->site_url['pass'])
						{
							$related = false;
						}
					}
					/*else if ( isset($this->site_url['pass']) )
					{
						$related = false;
					}*/
					
					if ($related)
					{
						unset($url['host'], $url['user'], $url['pass']);
					}
				}
				else if ( isset($url['port']) )
				{
					if ($url['port'] === $this->get_default_port($scheme))
					{
						unset($url['port']);
					}
				}
			}
			else if ( isset($url['port']) )
			{
				if ($url['port'] === $this->get_default_port($scheme))
				{
					unset($url['port']);
				}
			}
		}
		
		if ( !isset($url['host']) )
		{
			$url['path_relative_array'] = $this->relate_path($url['path_array']);
			$url['path_relative']       = $this->implode_path($url['path_relative_array'], false);
		}
		
		return $this->build_url($url, $output_type);
	}
	
	
	
	protected function remove_www($host)
	{
		if (strpos($host, 'www.') === 0)
		{
			$host = substr($host, 4);
		}
		
		return $host;
	}
}



/*function absolute_to_relative_url($url, $ignore_www=true, $choose_shortest=true)
{
	return Absolute_to_Relative_URLs::instance()->relate_url($url, $ignore_www, $choose_shortest);
}*/



/*
	Return a URL relative to the current site URL.
	
	$ignore_www  :: optionally, ignore "www" subdomain
	$output_type :: optionally, return either a:
			0: root-relative URL (/child-of-root/etc/)
			1: path-relative URL (../child-of-parent/etc/)
			2: shortest possible URL (root- or path-relative)
*/
function absolute_to_relative_url($url, $ignore_www=false, $output_type=2)
{
	global $absolute_to_relative_url_instance;
	
	if (!isset($absolute_to_relative_url_instance))
	{
		$absolute_to_relative_url_instance = new Absolute_to_Relative_URLs();
	}
	
	return $absolute_to_relative_url_instance->relate_url($url, $ignore_www, $output_type);
}



?>