PHP programming basics isset and empty-PHP Tutorial-php.cn

PHP programming basics isset and empty

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Release： 2016-07-25 08:58:05

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This article introduces the two most commonly used functions isset and empty in the basics of PHP programming, and gives a few examples for your reference.

In basic PHP programming, the two most commonly used functions are the isset function and the empty function. Examples are as follows:

<?php
/**
* empty函数与isset函数用例
* edit bbs.it-home.org
*/
    $arr[] = '';
    $arr[] = 0;
    $arr[] = NULL;
    $arr[] = null;
    $arr[] = '0';
    $arr[] = ' ';

    echo "isset\tempty\n";
    echo "-------------------------------\n";
    foreach ($arr as $key => $val)
    {
        echo isset($val) ? 'true': 'false';
        echo "\t";
        echo empty($val) ? 'true': 'false';
        echo "\n";
    }
?>

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Output result: isset empty ---------------------------------- true true true true false true false true true true true false Sometimes when entering a form, especially when configuring, filling in 0 means that the value is 0, but not filling in a value means that the value may be undefined. In this case, the following function can be used to judge:

<?php
    /**
     * 判断值是否为空
     *
     * 在php中,0,null,array()和''用empty函数判断时都会返回true, 但实际上很多情况下0是不应当被认为是空
     * 的。比如在设置参数值时，0可能表示值真的是0，而空字符串则可能表示该值未设置
     *
     * @site bbs.it-home.org
     * @param mixed $value 变量值
     * @param boolean $is_trim 是否要去掉前后空格
     * @return boolean
     */
    function isEmpty($value, $is_trim = false)
    {
        return $value === null || $value === array() || $value === '' || ($is_trim && is_scalar($value) && trim($value) === '');
    }

    echo isEmpty(0) ? '1':'0';
    echo isEmpty('0') ? '1':'0';
?>

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Output result: 00 You can see that entering 0 is no longer considered empty, regardless of whether it is a character or a number.

How about it? With the above two examples, do you have a deeper love for the PHP function isset and empty function? !