PHP数组-括号 [英] PHP Array - brackets
问题描述
在创建PHP数组时是否有人知道[]的含义，以及是否确实需要。因为从我的角度来看。两种方法都足够了。
does someone know the meaning of the [ ] in the creation of a PHP array, and if it's really needed. Becasuse from my point of view. Both ways are sufficinent
方法1，带括号：
$cars[] = array ('expensive' => $BMW,
'medium' => $Volvo,
'cheap' => $Lada);
方式2，不带括号：
$cars = array ('expensive' => $BMW,
'medium' => $Volvo,
'cheap' => $Lada);
推荐答案
阅读 http://php.net/manual/en/function.array-push.php 差异。
主要区别：
- 引用
array（）仅在创建变量时才能完成。 - $ var []可以将值添加到已经存在的数组中。
- $ var []将创建一个数组，并且实际上与
$ var 相同的函数调用 = array（...）;
- citing
array()can only be done when creating the variable. - $var[] can add values to arrays that already exist.
- $var[] will create an array and is in effect the same function call as
$var = array(...);
还
- 您不能使用
$ var []方法在单个声明中分配多个值（请参见下面的示例4， ）。
- You can not assign multiple values in a single declaration using the
$var[]approach (see example 4, below).
一些工作过程：
1） 使用 array（）
1) Using array()
$cars = "cats";
$cars = array("cars","horses","trees");
print_r($cars) ;
会输出
$cars --> [0] = cars
[1] = horses
[2] = trees
2）附加值
然后写 $ cars = array（ goats）; 不会附加值，而是初始化一个新数组，给出：
Then writing $cars = array("goats"); will NOT append the value but will instead initialise a NEW ARRAY, giving:
$cars --> [0] = goats
但是如果使用方括号附加，则写 $ cars [] =山羊 会给您：
But if you use the square brackets to append then writing $cars[] = "goats" will give you :
$cars --> [0] = cars
[1] = horses
[2] = trees
[3] = goats
您的原始问题意味着 = 符号右侧的任何内容将附加到当前数组（如果左侧）手侧的语法为 $ var [] ，但这将附加为数字。如上图所示。
Your original question means that whatever is on the right hand side of the = sign will be appended to current array, if the left hand side has the syntax $var[] but this will be appended Numerically. As shown above.
您可以通过填写键值来按键名附加事物： $ cars ['cheap'] = $ Lada; 。
You can append things by key name by filling in the key value: $cars['cheap'] = $Lada; .
您的示例1设置了一个数组保存在数组中，因此要访问值$ Lada，您应引用 $ cars [0] ['cheap'] 。示例2设置了数组，但是将覆盖任何现有的数组或变量中的值。
Your example 1 is setting that an array is held within an array, so to access the value $Lada you would reference $cars[0]['cheap'] . Example 2 sets up the array but will overwrite any existing array or value in the variable.
3）字符串和数字索引
使用 array（...）语法非常适合在数组创建时定义多个值时，这些值具有非数字或数字非线性键，例如您的示例：
The method of using the array(...) syntax is good for defining multiple values at array creation when these values have non-numeric or numerically non-linear keys, such as your example:
$cars = array ('expensive' => "BMW",
'medium' => "Volvo",
'cheap' => "Lada");
将以以下数组输出：
$cars --> ['expensive'] = BMW
['medium'] = Volvo
['cheap'] = Lada
但是，如果您使用以下语法：
But if you used the alternative syntax of:
$cars[] = "BMW";
$cars[] = "Volvo";
$cars[] = "Lada";
这将输出：
$cars --> [0] = BMW
[1] = Volvo
[2] = Lada
4）我还在写......
再举一个例子：您可以结合使用<$ c $的效果c> array（）和 $ var [] ，并在方括号内包含键声明：
As another example: You can combine the effects of using array() and $var[] with key declarations within the square brackets thus:
$cars['expensive'] = "BMW";
$cars['medium'] = "Volvo";
$cars['budget'] = "Lada";
给予：
$cars --> ['expensive'] = BMW
['medium'] = Volvo
['cheap'] = Lada
（我的原始答案很冗长，但不是很好）。
(my original answer was verbose and not very great).
5）最后.....
那么当您结合这两种样式，将 array（）声明与 $ var [] 附加项混合在一起：
So what happens when you combine the two styles, mixing the array() declaration with the $var[] additions:
$ray = array("goats" => "horny", "knickers" => "on the floor", "condition" => "sour cream");
$ray[] = "crumpet";
$ray[] = "bread";
这将同时维护数组中的数字和字符串键索引，并以输出print_r（）：
This will maintain both numeric and string key indexes in the array, outputting with print_r():
$ray --> [goats] => horny
[knickers] => on the floor
[condition] => sour cream
[0] => crumpet
[1] => bread
这篇关于PHP数组-括号的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
