phpº¯ÊýissetºÍemptyµÄÇø±ð

if(isset($var)){
print '$var value is not null.';
}else {
print '$var value is null.';
}

if(empty($var)){
print '$var value is empty.';
}else{
print '$var value is not empty.';
}
ÔËÐиóÌÐò£¬²âÊÔ½á¹ûΪ $var value is empty.      $var value is null.
ÔÚ³ÌÐòÇ°¼ÓÈë$var = '';»ò$var = 0; ²âÊÔ½á¹ûΪ $var value is empty.      $var value is not null.
ÔÚ³ÌÐòÇ°¼ÓÈë$var = 'aaaa';»ò$var = 32;²âÊÔ½á¹ûΪ $var value is not empty.      $var value is not null.
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issetº¯Êý½ö½ö²âÊԸñäÁ¿ÊÇ·ñ±»¶¨Òå¹ý¡£isdef or not.
emptyº¯ÊýÔò²âÊԸñäÁ¿ÊÇ·ñΪ¿Õ£¬Èçnull,'',0¶¼Îª¿Õ¡£