智能PHP压缩代码

Question

所以,我看到了"编程难题和代码高尔夫"这个聪明的话题:我们不是陌生人.......最好的答案是PHP代码打印Never Gonna Give You Up的歌词.它只有543个字节.

我试图理解这个PHP代码,但我无法理解这是如何工作的.我认为这是一种基于语法的压缩,但我不知道如何使用未声明的常量

<?php range('-', T);

所以这是代码.这是如何运作的？

<?=str_replace(range('-',T),split(q,"
I justCannaLE?2Gotta >u=Msta=.q
Ng1Nlet? downNrun<rH=5desMt?N>cryNsayRoodbyeNtE< lie5hurt?q

We'T3n each@Jor s8lSg6r hear9<ch: but6;Lo7hyL7BInsideCe both3Cha9Ro: S
We3KeRa45we;QplBq1)O)NgiT, nPgiT
(GqiT? upq howFJeel:
q knowqmeq<= q
YHq8sqo qt's beenqingq'req aqndqmake? q yHq othMqAqay it
q wqDqellq I'mqGqouqIq fqLhq tqerq
NPq
(OohqeTrQqRSna q gqonqve"),"We; n7trangMsL8loT63Ke rules5s8d8I
AJull commit4nt'sChatFKink: of6CHldn'tRetKisJrom<ny@Ruy-/A= if?<sk 42DS'tLE 4?;Lo8bli=L7ee..
O,R1)O,R001)/-..");

看到它在Ideone上工作.

Answer 1

让我们str_replace一个一个地分析参数.

range('-',T)

该range()函数返回一个数组,该数组具有从第一个参数到第二个参数的元素.字符由ASCII值来考虑,结果是

Array
(
    [0] => -
    [1] => .
    [2] => /
    [3] => 0
    [4] => 1
    [5] => 2
    [6] => 3
    [7] => 4
    [8] => 5
    [9] => 6
    [10] => 7
    [11] => 8
    [12] => 9
    [13] => :
    [14] => ;
    [15] => <
    [16] => =
    [17] => >
    [18] => ?
    [19] => @
    [20] => A
    [21] => B
    [22] => C
    [23] => D
    [24] => E
    [25] => F
    [26] => G
    [27] => H
    [28] => I
    [29] => J
    [30] => K
    [31] => L
    [32] => M
    [33] => N
    [34] => O
    [35] => P
    [36] => Q
    [37] => R
    [38] => S
    [39] => T
)

为什么T而不是"T"？PHP有一个错误,它使未定义的常量作为与常量名称具有相同内容的字符串进行评估.常量T未定义,因此它与"T"为代码高尔夫目的保存两个字符相同.这同样适用于q后.如果服务器上有错误报告,则会显示有关未定义常量的警告.

split(q,"I justCannaLE?2Gotta >u=Msta=.q...");

这会将字符串拆分为字符处的数组q.同样,这使得代码比使用数组文字更短.结果:

Array
(
    [0] => 
I justCannaLE?2Gotta >u=Msta=.
    [1] => 
Ng1Nlet? downNrun<rH=5desMt?N>cryNsayRoodbyeNtE< lie5hurt?
    [2] => 

We'T3n each@Jor s8lSg6r hear9<ch: but6;Lo7hyL7BInsideCe both3Cha9Ro: S
We3KeRa45we;QplB
    [3] => 1)O)NgiT, nPgiT
(G
    [4] => iT? up
    [5] =>  howFJeel:

    [6] =>  know
    [7] => me
    [8] => <= 
    [9] => 
YH
    [10] => 8s
    [11] => o 
    [12] => t's been
    [13] => ing
    [14] => 're
    [15] =>  a
    [16] => nd
    [17] => make? 
    [18] =>  yH
    [19] =>  othM
    [20] => A
    [21] => ay it

    [22] =>  w
    [23] => D
    [24] => ell
    [25] =>  I'm
    [26] => G
    [27] => ou
    [28] => I
    [29] =>  f
    [30] => Lh
    [31] =>  t
    [32] => er
    [33] => 
NP
    [34] => 
(Ooh
    [35] => eTrQ
    [36] => RSna 
    [37] =>  g
    [38] => on
    [39] => ve
)

最后一个参数是目标字符串.

"We; n7trangMsL8loT63Ke rules5s8d8I
AJull commit4nt'sChatFKink: of6CHldn'tRetKisJrom<ny@Ruy-/A= if?<sk 42DS'tLE 4?;Lo8bli=L7ee..
O,R1)O,R001)/-.."

如果将数组传递给str_replace()needle和haystack,则一次更换一个.为简单起见,让我们把它"We; n7trangMs"作为taget字符串并开始替换;.替换后的第一个步骤"7"与"8s"(第二阵列中的相应的替换):

"We; n8strangMs"

然后更换"8"与"o "

"We; no strangMs"

";" 同 "'re"

"We're no strangMs"

"M" 同 "er"

"We're no strangers"

简而言之,它是一种基本的压缩算法,您可以在其中找到在原始文本中重复的字符序列,并用单个字符替换它们.解压缩时,该字符将替换为原始序列.通过迭代运行进度,您可以再次压缩一次压缩的文本("o s"=> "8s"=> "7").