如何使用Imagick :: $ variable而不是Composite_Multiply

Question

我想添加Blendmode变量而不是COmposite_Multiply，您能告诉我如何获取它。

我也收到此错误，致命错误：访问未声明的静态属性：imagick :: $ this

  $ShortSleeveComposite = new CompositeImages;
  $ShortSleeveComposite->Image1 = $LongSleeveCompositeIMG;
  $ShortSleeveComposite->Image2 = $ShortSleeve;
  $ShortSleeveComposite->BlendMode = "COMPOSITE_MULTIPLY";

Class CompositeImages {

    public $Image1;
    public $Image2;
     public $BlendMode;  //Blendmode has COmposite_multiply value in it
     public function CreateComposite() {
        $Image1IMobj = new Imagick();
        $Image2IMobj = new Imagick();
         $Image1IMobj->readImageBlob($this->Image1);
        $Image2IMobj->readImageBlob($this->Image2);
       $Image1IMobj->compositeImage($Image2IMobj, Imagick::$this->BlendMode, $this->X_Coordinate, $this->Y_Coordinate);
    }