php笔记(6)

isset();检测变量是否设置,返回值boolean

$name=123;
var_dump(isset($name));//true

unset();释放(删除)变量;没有返回值

$name=123;
unset($name);

empty();检测一个变量是否为空;返回boolean值

$name=0;
var_dump(empty($name));//true

strlen();返回字符串长度

$name='12345';
echo strlen($name);//5