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如何检查一个变量是否被设置,并且值为NULL

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Release: 2016-06-06 20:34:38
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最近有一个小问题,就是如何在php中检查一个变量是否被设置并且值为null,看看大家都有什么好的解决方案?谢谢~~

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最近有一个小问题,就是如何在php中检查一个变量是否被设置并且值为null,看看大家都有什么好的解决方案?谢谢~~

$a=isset($a)?$a:null;

<code>isset($value)
is_null($value)


$value = null;

//!isset($value) && is_null($value)
if(!isset($value)) {
    if(is_null($value)) {
        echo '设置1:'.$value;
    } else {
        echo '未设置';
    }
} else {
    echo '设置2:'.$value;
}

</code>
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