PHP隐式通过引用传递？

Question

我有这个类，它将给定图像的大小调整为设定大小，并且还可以在其上放置水印（图章）。

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我的问题是在使用WaterMark（）函数后，为什么 class Picture { private $src_path, $src_image, $width, $height, $resized_image; public function __construct($src_path) { if (!file_exists($src_path)) { throw new InvalidArgumentException('Invalid image path!'); } $this->src_path = $src_path; $this->loadImage(); } private function loadImage() { if (exif_imagetype($this->src_path) == IMAGETYPE_JPEG) { $this->src_image = imagecreatefromjpeg($this->src_path); } elseif (exif_imagetype($this->src_path) == IMAGETYPE_PNG) { $this->src_image = imagecreatefrompng($this->src_path); } else { throw new InvalidArgumentException('Your image type is not JPEG or PNG!'); } } public function waterMark() { $stamp = imagecreatefromjpeg('C:\Users\Public\Pictures\Sample Pictures\resized.jpg'); $im = $this->resized_image; $marge_right = 10; $marge_bottom = 80; $sx = imagesx($stamp); $sy = imagesy($stamp); // Copy the stamp image onto our photo using the margin offsets and the photo // width to calculate positioning of the stamp. imagecopy($im, $stamp, imagesx($im) - $sx - $marge_right, imagesy($im) - $sy - $marge_bottom, 0, 0, imagesx($stamp), imagesy($stamp)); } public function resizeImage($w, $h) { list($width, $height) = getimagesize($this->src_path); $ratio = $width / $height; if ($w / $h > $ratio) { $new_width = $h * $ratio; $new_height = $h; }else { $new_height = $w / $ratio; $new_width = $w; } $this->resized_image = imagecreatetruecolor($new_width, $new_height); imagecopyresampled($this->resized_image, $this->src_image, 0, 0, 0, 0, $new_width, $new_height, $width, $height); } public function saveImage($quality, $destination = null) { if (!$destination) { $length = strlen($this->src_path) - strlen((string) $this->src_image); $destination = substr($this->src_path, 0, $length-3).'resized.jpg'; } return imagejpeg($this->resized_image, $destination, $quality); } } $pic = new Picture('C:/Users/Public/Pictures/Sample Pictures/Chrysanthemum.jpg'); $pic->resizeImage(400, 400); $pic->saveImage(100, 'C:/Users/Public/Pictures/ResizedImage.jpg'); $pic->waterMark(); //Why is the original picture ($this->resized_image) //is now watermarked ? //Why is there a reference here ? $pic->saveImage(100, 'C:/Users/Public/Pictures/WhyAmIWaterMarked.jpg'); 变量会更改为WaterMarked变量的值？

$this->resized_image

结果：

我写了另一个类来测试这种行为：

$im = $this->resized_image;
imagecopy($im, $stamp, imagesx($im) - $sx - $marge_right, imagesy($im) - $sy - $marge_bottom, 0, 0, imagesx($stamp), imagesy($stamp));

但结果如预期： 15,15,15;

那么，如果变量（class TestReference { public $foo; function setFoo($value) { $this->foo = $value; } function getFoo() { return $this->foo; } function getFooBar() { $tmp = $this->foo; $tmp = 20; return $this->foo; } } $bar = new TestReference(); $bar->setFoo(15); echo $bar->getFoo().'<br/>'; echo $bar->getFooBar().'<br/>'; echo $bar->getFoo().'<br/>'; ）被临时变量覆盖，那么Picture类怎么来呢？