php手动释放内存

<?php$s = str_repeat('1',1024); $b = &$s;$m=memory_get_usage(); //获取当前占用内存echo $m."\n";//unset($s);//$s = null;$mm = memory_get_usage(); //unset()后再查看当前占用内存echo $mm . "\n";echo $m -$mm ;echo "\n";?>

结论：

1, unset只是变量计数器减1，,当计数器为0的时候会触发回收

2, $s=null 会直接触发回收