PHP ランダム文字生成

Question

10桁のランダム文字を生成しています

生成された文字の始めが必ずアルファベットになるようにするにはどうしたらいいでしょうか？

●m14r2ohbxl
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<?php
$str=["0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"];
$y="";
$s=count($str)-1;
for($i=0;$i<10;$i++){
$y.=$str[rand(0,$s)];
}
echo $y;
?>

Comments

[BeatStar]

質問にあるコードだとどうなるのでしょうか。

プログラムは書かれた通りにしか動きません。

[退会済みユーザー]

何に使う文字列なんでしょうか？
生成される文字列に暗号学的な安全性が求められる場合、rand() だとまずいです。

Answer 1

別の考え方として、初回とそれ以降で文字の候補を変えるってのもあります。

<?php
$str = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"];
$y = $str[rand(0, count($str) - 1)];
$str = ["0","1","2","3","4","5","6","7","8","9"] + $str;
$s = count($str) - 1;
for ($i=0; $i<9; $i++) {
    $y .= $str[rand(0, $s)];
}
echo $y;
?>

Answer 2

• 一番最初のrand関数を実行する際の引数を $s - 10にする。
• $strの配列を参照する際に、添え字に+10する。

このようにすると文字を選ぶ際に最初の10要素を飛ばせます。

つまり、1文字目だけこのようにすれば良いでしょう。

$y.=$str[rand(0,$s -10) +10];

Comments

[poppi]

ありがとうございます
下記のようにさせていただきました
なにか問題点があればご指摘いただけると助かります

<?php
$str=["0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"];
$y="";
$s=count($str)-1;
for($i=0;$i<10;$i++){
if($i==0){
$y.=$str[rand(0,$s -10) +10];
}else{
$y.=$str[rand(0,$s)];
}
}
echo $y;
?>

[hope_mucci]

特に問題ないのではないでしょうか。
十分テストはしてくださいね。