php中compact,extract,list函数的使用

<?php//compact 将变量组合为数组$key_1 = "val_1";$key_2 = "val_2";$data = array('$key_3'=>'val_3','$key_4'=>'val_4');$arr_n =compact('key_1','key_2','data');echo "compact:\n";//extract根据键名导出变量echo "extract:\n";$arr_str = array('key_a'=>'val_a','key_b'=>'val_b','key_arr'=>array('1','2','3'));extract($arr_str);var_dump($key_a);var_dump($key_b);var_dump($key_arr);// list(只作用于索引数组)用来取出数据。可只取出部分数据，如只取出前两个echo "list:\n";$arr_data =array('data_1','data_2','data_3','data_4');list($v1,$v2)=$arr_data;var_dump($v1);var_dump($v2);//list也可取变量放在数组指定位置中list($data_res['0'],$data_res['5'])=$arr_data;var_dump($data_res); ?>