Webmozart\Expression\Selector\Key::toString PHP Method

    public function toString()
    {
        $exprString = $this->expr->toString();
        if ($this->expr instanceof AndX || $this->expr instanceof OrX) {
            return $this->key . '{' . $exprString . '}';
        }
        // Append "functions" with "."
        if (isset($exprString[0]) && ctype_alpha($exprString[0])) {
            return $this->key . '.' . $exprString;
        }
        return $this->key . $exprString;
    }

 public function testToString()
 {
     $expr1 = new Key('name', new GreaterThan(10));
     $expr2 = new Key('name', new EndsWith('.css'));
     $expr3 = new Key('name', new AndX(array(new GreaterThan(10), new EndsWith('.css'))));
     $this->assertSame('name>10', $expr1->toString());
     $this->assertSame('name.endsWith(".css")', $expr2->toString());
     $this->assertSame('name{>10 && endsWith(".css")}', $expr3->toString());
 }