如何在PHP中使用正则表达式查找和替换两个标签之间的字符串？

Question

If we have a text like this:

[SYS 1]Page 1 from 2:[/SYS]

Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard ...

[SYS 2]Page 2 from 2:[/SYS]

It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged.

How should I keep only text between [SYS] and [/SYS] tags? like this:

Page 1 from 2:

Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard ...

Page 2 from 2:

It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged.

I think the following regex would find the text inside two tags without attributes:

/\[SYS\](.+?)\[\/SYS\]/

But how should I replace the entire element with the inner text (or any other string) for that tag?

Answer 1

Use the following expression:

\[SYS[^]]*\](.+?)\[/SYS\]

And replace with $1 , see a demo on regex101.com .

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In PHP :

 $regex = '~\\[SYS[^]]*\\](.+?)\\[/SYS\\]~'; $string = preg_replace($regex, '$1', $your_original_string); 

See a demo for the complete code on ideone.com .

Answer 2

You can replace like so:

$re = "/\\[\\/?SYS(?:\\s\\d+)?\\]/";
$str = "[SYS 1]Page 1 from 2:[/SYS]";
echo preg_replace($re, "", $str)