is_numeric

    (PHP 4, PHP 5, PHP 7, PHP 8)

    is_numeric — 检测变量是否为数字或数字字符串

    说明

    is_numeric(mixed$value): bool

    检测指定的变量是否为数字或数字字符串。

    参数

    value

    需要检测的变量。

    返回值

    如果 value 是数字或数字字符串， 返回 true，否则返回 false。

    更新日志

    版本说明
    8.0.0 以空格结尾的数字字符串（"42 "）现在将返回 true。以前，会返回 false。

    示例

    示例 #1 is_numeric() 示例

    <?php
    $tests     = array(
    "42",
    1337,
    0x539,
    02471,
    0b10100111001,
    1337e0,
    "0x539",
    "02471",
    "0b10100111001",
    "1337e0",
    "not numeric",
    array(),
    9.1,
    null,
    '',
    );

    foreach (    $tests as $element) {
    if (    is_numeric($element)) {
    echo     var_export($element, true) . " is numeric", PHP_EOL;
    } else {
    echo     var_export($element, true) . " is NOT numeric", PHP_EOL;
    }
    }
    ?>

    以上示例会输出：

    '42' is numeric 1337 is numeric 1337 is numeric 1337 is numeric 1337 is numeric 1337.0 is numeric '0x539' is NOT numeric '02471' is numeric '0b10100111001' is NOT numeric '1337e0' is numeric 'not numeric' is NOT numeric array ( ) is NOT numeric 9.1 is numeric NULL is NOT numeric '' is NOT numeric

    示例 #2 带有空格的 is_numeric()

    <?php
    $tests     = [
    " 42",
    "42 ",
    "\u{A0}9001", // non-breaking space
    "9001\u{A0}", // non-breaking space
    ];
    foreach (    $tests as $element) {
    if (    is_numeric($element)) {
    echo     var_export($element, true) . " is numeric", PHP_EOL;
    } else {
    echo     var_export($element, true) . " is NOT numeric", PHP_EOL;
    }
    }
    ?>

    以上示例在 PHP 8 中的输出：

    ' 42' is numeric '42 ' is numeric ' 9001' is NOT numeric '9001 ' is NOT numeric

    以上示例在 PHP 7 中的输出：

    ' 42' is numeric '42 ' is NOT numeric ' 9001' is NOT numeric '9001 ' is NOT numeric

    参见

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