使用正则表达式修剪多行字符串并缩小空格 [英] trim lines and shrink whitespaces using regex for multi line string

问题描述

我正在使用 php函数 创建一个函数来修剪多行字符串中所有不必要的空格.

I'm using a php function want to create a function to trim all unnecessary white spaces from a multi line string.

不起作用的正则表达式是最后删除空格的正则表达式:

The regex that it's not working is the one that removes spaces at the end:

// Always trim at the end. Warning: this seems to be the costlier
// operation, perhaps because looking ahead is harder?
$patterns[] = ['/ +$/m', ''];

从文本区域给出以下字符串:

Given the following string from a textarea:

 first  line... abc   //<-- blank space here
 second  is  here... def   //<-- blank space here
 //<-- blank space here
 fourth  line... hi  there   //<-- blank space here

 sith  is  here....   //<-- blank space here

每行的开头和结尾都有空格，单词之间也有多个空格.

There are blank spaces at the beginning and end of each line plus more than one between the words.

运行函数后:

$functions->trimWhitespace($description, ['blankLines' => false]);

这就是我得到的:

first line... abc //<-- blank space here
second is here... def //<-- blank space here
//<-- no bank space here
fourth line... hi there //<-- blank space here

sith is here....//<-- no blank space here

为什么只从最后一行删除尾随空格?

Why is it only removing the trailing space from the last line?

推荐答案

您可以使用(*ANYCRLF)动词重新定义$匹配的位置.

You may redefine where $ matches using the (*ANYCRLF) verb.

请参见以下 PHP演示:

$s = " ddd    \r\n  bbb     ";
$n = preg_replace('~(*ANYCRLF)\h+$~m', '', $s); // if the string can contain Unicode chars,
echo $n;                                        // also add "u" modifier ('~(*ANYCRLF)\h+$~um')

详细信息:

• (*ANYCRLF)-指定换行符:(*CR)，(*LF)或(*CRLF)
• \h+-1+ 水平空白字符
• $-行尾(现在，在CR或LF之前)
• ~m-启用多行模式($在行尾匹配).

• (*ANYCRLF) - specifies a newline convention: (*CR), (*LF) or (*CRLF)
• \h+ - 1+ horizontal whitespace chars
• $ - end of line (now, before CR or LF)
• ~m - multiline mode on ($ matches at the end of a line).

如果要允许$在任何Unicode换行符处匹配，请将(*ANYCRLF)替换为(*ANY).

If you want to allow $ to match at any Unicode line breaks, replace (*ANYCRLF) with (*ANY).

请参见 PCRE参考中的 Newline conventions :

See Newline conventions in the PCRE reference:

(*CR)        carriage return
(*LF)        linefeed
(*CRLF)      carriage return, followed by linefeed
(*ANYCRLF)   any of the three above
(*ANY)       all Unicode newline sequences

现在，如果您需要

• 修剪开始和结束的行
• 将行内的空格缩小为一个空格

使用

$s = " Ł    ę  d    \r\n  Я      ёb     ";
$n = preg_replace('~(*ANYCRLF)^\h+|\h+$|(\h){2,}~um', '$1', $s);
echo $n;

请参见 PHP演示.

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