PHPでアレイとForeachの学習

※ ソースコードを見やすくするために、Syntaxhilighterを使っています。状況によって表示に時間がかかる場合があります。

php.orgのマニュアルを参考にアレイとforeachのお勉強をしました。
http://php.net/manual/en/language.operators.string.php

$low = 1; $high = 30; $step =1;
$i = range($low, $high, $step);

print_r ($i);
echo "

";

// リファレンスとして使用しないと、アレイ$iの要素はそれぞれ2倍とならない
foreach ($i as $value){
 $value = $value * 2 ;
}
print_r($i);

echo "

";

// リファレンス使用で、アレイ$iの要素はそれぞれ2倍となる
foreach ($i as &$value){
 $value = $value * 2 ;
}
print_r($i);

unset($value)

アレイ$iのアウトプットは、それぞれ次のようになります。

オリジナル
Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 5 [5] => 6 [6] => 7 [7] => 8 [8] => 9 [9] => 10 [10] => 11 [11] => 12 [12] => 13 [13] => 14 [14] => 15 [15] => 16 [16] => 17 [17] => 18 [18] => 19 [19] => 20 [20] => 21 [21] => 22 [22] => 23 [23] => 24 [24] => 25 [25] => 26 [26] => 27 [27] => 28 [28] => 29 [29] => 30 )

---

2倍となっていない
Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 5 [5] => 6 [6] => 7 [7] => 8 [8] => 9 [9] => 10 [10] => 11 [11] => 12 [12] => 13 [13] => 14 [14] => 15 [15] => 16 [16] => 17 [17] => 18 [18] => 19 [19] => 20 [20] => 21 [21] => 22 [22] => 23 [23] => 24 [24] => 25 [25] => 26 [26] => 27 [27] => 28 [28] => 29 [29] => 30 )

---

2倍となった
Array ( [0] => 2 [1] => 4 [2] => 6 [3] => 8 [4] => 10 [5] => 12 [6] => 14 [7] => 16 [8] => 18 [9] => 20 [10] => 22 [11] => 24 [12] => 26 [13] => 28 [14] => 30 [15] => 32 [16] => 34 [17] => 36 [18] => 38 [19] => 40 [20] => 42 [21] => 44 [22] => 46 [23] => 48 [24] => 50 [25] => 52 [26] => 54 [27] => 56 [28] => 58 [29] => 60 )

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