php unset

php里面的unset 可以把值置空，但是并不会改变值已经有的索引位置

$testArr=array('frist','second','third');
echo '<pre>';
echo '<br/>---------------------------------proto ------------------------------</br>';
print_r($testArr);
foreach($testArr as $key=>$val){
    unset($testArr[$key]);
}
echo '<br/>---------------------opo---------------------------</br>';
print_r($testArr);
$testArr[]='good!';
echo '<br/>---------------------add---------------------------</br>';
print_r($testArr);
echo '</pre>';

If a static variable is unset() inside of a function, unset() destroys the variable only in the context of the rest of a function. Following calls will restore the previous value of a variable.

function foo()
{
    static $bar;
    $bar++;
    echo "Before unset: $bar, ";
    unset($bar);
    $bar = 23;
    echo "after unset: $bar<br/>";
}

foo();
foo();
foo();



vld分析：
function foos(&$bar) 
{
    unset($bar);
    $bar = "blah";
}

$bar = 'something';
echo "$bar<br/>";

foos($bar);
echo "$bar<br/>";

If a variable that is PASSED BY REFERENCE is unset() inside of a function, only the local variable is destroyed. The variable in the calling environment will retain the same value as before unset() was called.

这是手册中发现的，突然感觉把手册再翻一遍，是个正确的选择