为什么 Python 中的函数可以索引，而 PHP 中则不行？
我的意思并不是说这个问题是关于 Python 与 PHP 的，而是关于一般语言的。我使用 Python 和 PHP 作为示例，因为我了解它们。
在Python中，我们可以执行mytoken = mystring.split(mydelimiter)[1]，访问由str.split返回的列表，而无需将其分配给列表。 在 PHP 中，我们必须在访问数组之前将其放入内存中，如 $mytokenarray =explode($mydelimiter, $mystring); 所示。 $mytoken = $mytokenarray[1];。据我所知，不可能像Python那样用一条语句来做到这一点。
这种差异的背后到底发生了什么？
I don't mean for this question to be about Python vs PHP but about languages in general. I use Python and PHP as examples because I know them.
In Python we can do mytoken = mystring.split(mydelimiter)[1], accessing the list returned by str.split without ever assigning it to a list.
In PHP we must put the array in memory before accessing it, as in $mytokenarray = explode($mydelimiter, $mystring); $mytoken = $mytokenarray[1];. As far as I know it is not possible to do this in one statement as in Python.
What is going on behind this difference?
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如果您尝试在 php 中执行此操作，
请注意您收到的错误：
解析错误：语法错误，意外的“[”。这意味着 php 在尝试解析代码时会感到不安，而不是在尝试执行代码时。我怀疑这意味着 php 的语法（据我所知，它是动态生成的，尽管我真的不知道）说你不能在
statement或之后放置 '['表达式或者无论他们如何称呼它。相反，您可能只能将“[”放在变量后面。这是Python的语法。包含规则的 http://docs.python.org/reference/grammar.html
预告片：'(' [arglist] ')' | '['下标列表']' | '.' NAME从那里您可以看到trailer是atom的一部分，它也可以包含[。您开始意识到事情非常复杂。等等，长话短说，了解编译器，或者更好的是，为玩具语言编写一个编译器。然后你将对语言怪癖有大量的洞察力。
If you try to do this in php
notice the error you get:
Parse error: syntax error, unexpected '['.This means that php is getting upset when it tries to parse the code, not when it tries to execute it. I suspect that means that php's grammar (which, I hear rumored, is generated on the fly though I really have no idea) says that you can't put '[' after a
statementorexpressionor whatever they call it. Rather, you can probably only put '[' after a variable.Here's Python's grammar. http://docs.python.org/reference/grammar.html which contains the rule
trailer: '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAMEFrom there you can see thattraileris part ofatomwhich can also contain[. You're starting to get the picture that it's pretty complicated.Blah blah blah, long story short, learn about compilers, or even better, write one for a toy language. Then you will have loads of insight into language quirks.
这是语言作者选择做出的设计决策。一般来说（当然情况并非总是如此），语言的语法越好，它的速度就越慢。典型的例子：红宝石。
It is a design decision the authors of the languages chose to make. Generally spoken (and this is of course not always the case) the nicer the syntax a language has the slower it tends to be. Case in point: Ruby.
从 5.4 版开始，PHP 就可以实现此功能。
This feature is now possible with PHP as of version 5.4.