PHP中向对象数组添加元素的正确指南

<?php
class DNA {
    private $RSID;
    private $CHROMOSOME;

    public function setRSID($RSID) {
        $this->RSID = $RSID;
    }

    public function setCHROMOSOME($CHROMOSOME) {
        $this->CHROMOSOME = $CHROMOSOME;
    }

    public function getRSID() {
        return $this->RSID;
    }

    public function getCHROMOSOME() {
        return $this->CHROMOSOME;
    }
}
?>

<?php
// 错误的示例：这只创建了一个DNA对象，并将其引用放入数组的第一个位置
$dna1[] = new DNA; 

// 尝试为数组的多个索引设置属性，但它们都指向同一个对象（$dna1[0]）
$dna1[0]->setRSID(1);
$dna1[0]->setCHROMOSOME(2);

// 以下操作实际上会覆盖 $dna1[0] 所指向对象的属性，而不是创建新的对象
$dna1[1]->setRSID(5); // 错误：$dna1[1] 尚未被实例化，会导致错误或意外行为
$dna1[1]->setCHROMOSOME(3);

$dna1[2]->setRSID(7); // 错误
$dna1[2]->setCHROMOSOME(0); // 错误
?>

<?php
// 首先，声明一个空数组，这是一个良好的习惯
$dnaArray = [];

// 实例化第一个对象并添加到数组的索引0
$dnaArray[0] = new DNA;
$dnaArray[0]->setRSID(1);
$dnaArray[0]->setCHROMOSOME(2);

// 实例化第二个对象并添加到数组的索引1
$dnaArray[1] = new DNA;
$dnaArray[1]->setRSID(5);
$dnaArray[1]->setCHROMOSOME(3);

// 实例化第三个对象并添加到数组的索引2
$dnaArray[2] = new DNA;
$dnaArray[2]->setRSID(7);
$dnaArray[2]->setCHROMOSOME(0);

// 验证数组内容
echo "DNA 1: RSID=" . $dnaArray[0]->getRSID() . ", CHROMOSOME=" . $dnaArray[0]->getCHROMOSOME() . "\n";
echo "DNA 2: RSID=" . $dnaArray[1]->getRSID() . ", CHROMOSOME=" . $dnaArray[1]->getCHROMOSOME() . "\n";
echo "DNA 3: RSID=" . $dnaArray[2]->getRSID() . ", CHROMOSOME=" . $dnaArray[2]->getCHROMOSOME() . "\n";
?>

<?php
$dnaArray = []; // 初始化空数组

// 创建并添加第一个DNA对象
$dnaObject1 = new DNA;
$dnaObject1->setRSID(1);
$dnaObject1->setCHROMOSOME(2);
$dnaArray[] = $dnaObject1; // 使用 [] 动态添加

// 创建并添加第二个DNA对象
$dnaObject2 = new DNA;
$dnaObject2->setRSID(5);
$dnaObject2->setCHROMOSOME(3);
array_push($dnaArray, $dnaObject2); // 使用 array_push 动态添加

// 创建并添加第三个DNA对象
$dnaObject3 = new DNA;
$dnaObject3->setRSID(7);
$dnaObject3->setCHROMOSOME(0);
$dnaArray[] = $dnaObject3; // 再次使用 [] 动态添加

// 验证数组内容
foreach ($dnaArray as $index => $dna) {
    echo "DNA " . ($index + 1) . ": RSID=" . $dna->getRSID() . ", CHROMOSOME=" . $dna->getCHROMOSOME() . "\n";
}
?>

<?php
class DNA {
    private $RSID;
    private $CHROMOSOME;

    // 修改set方法使其返回$this，支持链式调用
    public function setRSID($RSID) {
        $this->RSID = $RSID;
        return $this; 
    }

    public function setCHROMOSOME($CHROMOSOME) {
        $this->CHROMOSOME = $CHROMOSOME;
        return $this;
    }

    public function getRSID() {
        return $this->RSID;
    }
    public function getCHROMOSOME() {
        return $this->CHROMOSOME;
    }
}

$dnaArray = [];

$dnaArray[] = (new DNA())->setRSID(1)->setCHROMOSOME(2);
$dnaArray[] = (new DNA())->setRSID(5)->setCHROMOSOME(3);
$dnaArray[] = (new DNA())->setRSID(7)->setCHROMOSOME(0);

// 验证数组内容
foreach ($dnaArray as $index => $dna) {
    echo "DNA " . ($index + 1) . ": RSID=" . $dna->getRSID() . ", CHROMOSOME=" . $dna->getCHROMOSOME() . "\n";
}
?>