检查变量在PHP中是否为整数

Question

我有以下代码

    $page = $_GET['p'];

    if($page == "")
    {
        $page = 1;
    }
    if(is_int($page) == false)
    {
        setcookie("error", "Invalid page.", time()+3600);
        header("location:somethingwentwrong.php");
        die();
    }
    //else continue with code

我将用它来查看数据库的不同“页面”（结果1-10、11-20等）。但是，我似乎无法使is_int（）函数正常工作。在网址（noobs.php？p =
1）中输入“ 1”会给我无效的页面错误，以及类似“ asdf”的错误。

Answer 1

使用is_numeric()检查，如果一个变量是一个整数是一个坏主意。该函数将返回TRUE用于3.14例如。这不是预期的行为。

要正确执行此操作，可以使用以下选项之一：

考虑此变量数组：

$variables = [
    "TEST 0" => 0,
    "TEST 1" => 42,
    "TEST 2" => 4.2,
    "TEST 3" => .42,
    "TEST 4" => 42.,
    "TEST 5" => "42",
    "TEST 6" => "a42",
    "TEST 7" => "42a",
    "TEST 8" => 0x24,
    "TEST 9" => 1337e0
];

# Check if your variable is an integer
if ( filter_var($variable, FILTER_VALIDATE_INT) === false ) {
  echo "Your variable is not an integer";
}

输出：

TEST 0 : 0 (type:integer) is an integer ✔
TEST 1 : 42 (type:integer) is an integer ✔
TEST 2 : 4.2 (type:double) is not an integer ✘
TEST 3 : 0.42 (type:double) is not an integer ✘
TEST 4 : 42 (type:double) is an integer ✔
TEST 5 : 42 (type:string) is an integer ✔
TEST 6 : a42 (type:string) is not an integer ✘
TEST 7 : 42a (type:string) is not an integer ✘
TEST 8 : 36 (type:integer) is an integer ✔
TEST 9 : 1337 (type:double) is an integer ✔

第二种选择（比较方式）：

# Check if your variable is an integer
if ( strval($variable) !== strval(intval($variable)) ) {
  echo "Your variable is not an integer";
}

输出：

TEST 0 : 0 (type:integer) is an integer ✔
TEST 1 : 42 (type:integer) is an integer ✔
TEST 2 : 4.2 (type:double) is not an integer ✘
TEST 3 : 0.42 (type:double) is not an integer ✘
TEST 4 : 42 (type:double) is an integer ✔
TEST 5 : 42 (type:string) is an integer ✔
TEST 6 : a42 (type:string) is not an integer ✘
TEST 7 : 42a (type:string) is not an integer ✘
TEST 8 : 36 (type:integer) is an integer ✔
TEST 9 : 1337 (type:double) is an integer ✔

第三种选择（CTYPE_DIGIT方式）：

# Check if your variable is an integer
if ( ! ctype_digit(strval($variable)) ) {
  echo "Your variable is not an integer";
}

输出：

TEST 0 : 0 (type:integer) is an integer ✔
TEST 1 : 42 (type:integer) is an integer ✔
TEST 2 : 4.2 (type:double) is not an integer ✘
TEST 3 : 0.42 (type:double) is not an integer ✘
TEST 4 : 42 (type:double) is an integer ✔
TEST 5 : 42 (type:string) is an integer ✔
TEST 6 : a42 (type:string) is not an integer ✘
TEST 7 : 42a (type:string) is not an integer ✘
TEST 8 : 36 (type:integer) is an integer ✔
TEST 9 : 1337 (type:double) is an integer ✔

第四个选项（REGEX方式）：

# Check if your variable is an integer
if ( ! preg_match('/^\d+$/', $variable) ) {
  echo "Your variable is not an integer";
}

输出：

TEST 0 : 0 (type:integer) is an integer ✔
TEST 1 : 42 (type:integer) is an integer ✔
TEST 2 : 4.2 (type:double) is not an integer ✘
TEST 3 : 0.42 (type:double) is not an integer ✘
TEST 4 : 42 (type:double) is an integer ✔
TEST 5 : 42 (type:string) is an integer ✔
TEST 6 : a42 (type:string) is not an integer ✘
TEST 7 : 42a (type:string) is not an integer ✘
TEST 8 : 36 (type:integer) is an integer ✔
TEST 9 : 1337 (type:double) is an integer ✔