Converting a Google search query to a PostgreSQL “tsquery”

("used cars" OR "new cars") -ford -mistubishi

('used cars' | 'new cars') & !ford & !mistubishi

((color:blue OR "4x4") OR style:coupe) -color:red used

WHERE to_tsvector(description) MATCH to_tsquery('used')
  AND color <> 'red'
  AND ( (color = 'blue' OR to_tsvector(description) MATCH to_tsquery('4x4') )
    OR style = 'coupe'
  );

<?php

ini_set( "display_errors", "on" );
error_reporting( E_ALL );

interface ILexer
{
    public function execute( $str );
    public function getTokens();
}

interface IParser
{
    public function __construct( iLexer $lexer );
    public function parse( $input );
    public function addToken( $token );
}

class GoogleQueryLexer implements ILexer
{
    private $tokenStack = array();

    public function execute( $str )
    {
    	$chars = str_split( $str );
    	foreach ( $chars as $char )
    	{
    		//	add to self::$tokenStack per your rules
    	}

    	//'("used cars" OR "new cars") -ford -mistubishi'
    	$this->tokenStack = array(
    			'('
    		,	'used cars'
    		,	'or new cars'
    		,	')'
    		,	'-ford'
    		,	'-mitsubishi'
    	);
    }

    public function getTokens()
    {
    	return $this->tokenStack;
    }
}

class GoogleQueryParser implements IParser
{
    protected $lexer;

    public function __construct( iLexer $lexer )
    {
    	$this->lexer = $lexer;
    }

    public function addToken( $token )
    {
    	$this->tokenStack[] = $token;
    }

    public function parse( $input )
    {
    	$this->lexer->execute( $input );
    	$tokens = $this->lexer->getTokens();

    	$expression = new QueryExpression();

    	foreach ( $tokens as $token )
    	{
    		$expression = $this->processToken( $token, $expression );
    	}

    	return $expression;
    }

    protected function processToken( $token, QueryExpression $expression )
    {
    	switch ( $token )
    	{
    		case '(':
    			return $expression->initiateSubExpression();
    			break;
    		case ')':
    			return $expression->getParentExpression();
    			break;
    		default:
    			$modifier	= $token[0];
    			$phrase		= substr( $token, 1 );
    			switch ( $modifier )
    			{
    				case '-':
    					$expression->addExclusionPhrase( $phrase );
    					break;
    				case '+':
    					$expression->addPhrase( $phrase );
    					break;
    				default:
    					$operator	= trim( substr( $token, 0, strpos( $token, ' ' ) ) );
    					$phrase		= trim( substr( $token, strpos( $token, ' ' ) ) );
    					switch ( strtolower( $operator ) )
    					{
    						case 'and':
    							$expression->addAndPhrase( $phrase );
    							break;
    						case 'or':
    							$expression->addOrPhrase( $phrase );
    							break;
    						default:
    							$expression->addPhrase( $token );
    					}
    			}
    	}
    	return $expression;
    }
}

class QueryExpression
{
    protected $phrases = array();
    protected $subExpressions = array();
    protected $parent;

    public function __construct( $parent=null )
    {
    	$this->parent = $parent;
    }

    public function initiateSubExpression()
    {
    	$expression = new self( $this );
    	$this->subExpressions[] = $expression;
    	return $expression;
    }

    public function getPhrases()
    {
    	return $this->phrases;
    }

    public function getSubExpressions()
    {
    	return $this->subExpressions;
    }

    public function getParentExpression()
    {
    	return $this->parent;
    }

    protected function addQueryPhrase( QueryPhrase $phrase )
    {
    	$this->phrases[] = $phrase;
    }

    public function addPhrase( $input )
    {
    	$this->addQueryPhrase( new QueryPhrase( $input ) );
    }

    public function addOrPhrase( $input )
    {
    	$this->addQueryPhrase( new QueryPhrase( $input, QueryPhrase::MODE_OR ) );
    }

    public function addAndPhrase( $input )
    {
    	$this->addQueryPhrase( new QueryPhrase( $input, QueryPhrase::MODE_AND ) );
    }

    public function addExclusionPhrase( $input )
    {
    	$this->addQueryPhrase( new QueryPhrase( $input, QueryPhrase::MODE_EXCLUDE ) );
    }
}

class QueryPhrase
{
    const MODE_DEFAULT = 1;
    const MODE_OR = 2;
    const MODE_AND = 3;
    const MODE_EXCLUDE = 4;

    protected $phrase;
    protected $mode;

    public function __construct( $input, $mode=self::MODE_DEFAULT )
    {
    	$this->phrase = $input;
    	$this->mode = $mode;
    }

    public function getMode()
    {
    	return $this->mode;
    }

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

class TsqueryBuilder
{
    protected $expression;
    protected $query;

    public function __construct( QueryExpression $expression )
    {
    	$this->query = trim( $this->processExpression( $expression ), ' &|' );
    }

    public function getResult()
    {
    	return $this->query;
    }

    protected function processExpression( QueryExpression $expression )
    {
    	$query = '';
    	$phrases = $expression->getPhrases();
    	$subExpressions = $expression->getSubExpressions();

    	foreach ( $phrases as $phrase )
    	{
    		$format = "'%s' ";
    		switch ( $phrase->getMode() )
    		{
    			case QueryPhrase::MODE_AND :
    				$format = "& '%s' ";
    				break;
    			case QueryPhrase::MODE_OR :
    				$format = "| '%s' ";
    				break;
    			case QueryPhrase::MODE_EXCLUDE :
    				$format = "& !'%s' ";
    				break;
    		}
    		$query .= sprintf( $format, str_replace( "'", "\'", $phrase ) );
    	}

    	foreach ( $subExpressions as $subExpression )
    	{
    		$query .= "& (" . $this->processExpression( $subExpression ) . ")";
    	}
    	return $query;
    }
}

$parser = new GoogleQueryParser( new GoogleQueryLexer() );

$queryBuilder = new TsqueryBuilder( $parser->parse( '("used cars" OR "new cars") -ford -mistubishi' ) );

echo $queryBuilder->getResult();