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compact

(PHP 4, PHP 5, PHP 7)

compact 建立一个数组,包括变量名和它们的值

说明

array compact ( mixed $varname1 [, mixed $... ] )

创建一个包含变量与其值的数组。

对每个参数,compact() 在当前的符号表中查找该变量名并将它添加到输出的数组中,变量名成为键名而变量的内容成为该键的值。简单说,它做的事和 extract() 正好相反。返回将所有变量添加进去后的数组。

任何没有变量名与之对应的字符串都被略过。

参数

varname1

compact() 接受可变的参数数目。每个参数可以是一个包括变量名的字符串或者是一个包含变量名的数组,该数组中还可以包含其它单元内容为变量名的数组, compact() 可以递归处理。

返回值

返回输出的数组,包含了添加的所有变量。

范例

Example #1 compact() 例子

<?php
$city  
"San Francisco";
$state "CA";
$event "SIGGRAPH";

$location_vars = array("city""state");

$result compact("event""nothing_here"$location_vars);
print_r($result);
?>

以上例程会输出:

Array
(
    [event] => SIGGRAPH
    [city] => San Francisco
    [state] => CA
)

注释

Note: Gotcha

因为可变变量也许不能在函数内部用于 PHP 的超全局数组,此时不能将超全局数组传递入 compact() 中。

参见

  • extract() - 从数组中将变量导入到当前的符号表

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User Contributed Notes 5 notes

up
99
tatarynowicz at gmail dot com
6 years ago
Please note that compact() will _not_ issue a warning if the specified variable name is undefined.
up
108
M Spreij
10 years ago
Can also handy for debugging, to quickly show a bunch of variables and their values:

<?php
print_r
(compact(explode(' ', 'count acw cols coldepth')));
?>

gives

Array
(
    [count] => 70
    [acw] => 9
    [cols] => 7
    [coldepth] => 10
)
up
33
Robc
6 years ago
The description says that compact is the opposite of extract() but it is important to understand that it does not completely reverse extract().  In particluar compact() does not unset() the argument variables given to it (and that extract() may have created).  If you want the individual variables to be unset after they are combined into an array then you have to do that yourself.
up
8
jmarkmurph at yahoo dot com
1 year ago
So compact('var1', 'var2') is the same as saying array('var1' => $var1, 'var2' => $var2) as long as $var1 and $var2 are set.
up
-49
piedone at pyrocenter dot hu
6 years ago
A quick way of compacting all local variables:

<?php
$localVariables
= compact(array_keys(get_defined_vars()));
?>

This is useful if you want to return all local variables from a function/method or you want to pass all local variables to one. A valid example would be to use this with application hooks/events (if you want the called hook to be able to modify everything in the caller), but otherwise use with care (as methods should be used through their declared interface).
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