$cwd= getcwd();//server root
getRelativePath($yourPathInput, $cwd)

function getRelativePath($filePathInput, $root){
	//$root= getcwd(); // get current working directory 
	$root= str_replace('\\','/',$root);// make all slashes forward
	$filePathInput= str_replace('\\','/',$filePathInput);// make all slashes forward
	$root = explode('/', $root);// root path array
	$filePathInput = explode('/', $filePathInput);//input file path array
	foreach($root as $level => $dir){
		if($dir === $filePathInput[$level]){
	  	unset($root[$level]);
			unset($filePathInput[$level]);
		}else{
			$levelPos= $levelPos."../";   
		}	
	}
	if(!$root){
	  $dirPath= implode('/', $filePathInput);// output down path
	}else{
	  $dirPath= $levelPos.implode('/', $filePathInput);// output up path
	}
	return $dirPath;
}