所以我在"编程谜题和代码高尔夫"上看到了这个聪明的话题：我们并不陌生。最好的答案是PHP代码打印Never Gonna Give You Up的歌词。它只有543字节长。
我试着理解这个PHP代码，但我不明白它是如何工作的。我认为这是一种基于语法的压缩，但我不知道如何使用中未声明的常量
<?php range('-', T);
这就是代码。这是怎么回事？
<?=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)/-..");
看看它在Ideone上的工作。
让我们逐一分析str_replace参数。
range('-',T)
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。字符按其ASCII值考虑，因此结果为
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有一个错误的特性，它将未定义的常量计算为与常量名称内容相同的字符串。常量T没有定义，因此它与"T"相同，后者保存两个字符用于代码高尔夫球。稍后q也是如此。如果服务器上有错误报告，它将显示关于未定义常量的警告。
split(q,"I justCannaLE?2Gotta >u=Msta=.q...");
这会将字符串拆分为一个q字符的数组。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)/-.."
如果将数组作为针和干草堆传递给str_replace()，则每次替换一个。为了简单起见，让我们只取"We; n7trangMs"作为taget字符串，并从;开始替换。将"7"替换为"8s"后的第一步（第二阵列中的相应替换）：
"We; n8strangMs"
然后用"o " 替换"8"
"We; no strangMs"
";"与"'re"
"We're no strangMs"
"M"与"er"
"We're no strangers"
简而言之，这是一种基本的压缩算法，可以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，您可以再次压缩压缩过的文本（"o s"=>"8s"=>"7"）。
试试吧！
未定义的常量假定为字符串。这就是启用通知后的样子：
Notice: Use of undefined constant T - assumed 'T' in D:'www'htdocs'test'index.php on line 1
Notice: Use of undefined constant q - assumed 'q' in D:'www'htdocs'test'index.php on line 1
Deprecated: Function split() is deprecated in D:'www'htdocs'test'index.php on line 12
We're no strangers to love
You know the rules and so do I
[...]
Never gonna say goodbye
Never gonna tell a lie and hurt you