preg_replace("/\[b\](.*)\[\/b\]/Usi", "<strong>$1</strong>", "Some text here... [b][b]Hello, [b]PHP![/b][/b][/b] ... [b]and here[/b]");
返回
Some text here... <strong>[b]Hello, [b]PHP!</strong>[/b][/b] ... <strong>and here</strong>
但我需要替换所有 [b]...[/b] 标签。为什么我的情况没有发生这种情况?
最佳答案
是的,如果元素是嵌套的,则需要多遍方法。这可以通过以下两种方式之一来完成;从内到外或从外到内匹配。这里有两个经过测试的脚本,带有完整注释的正则表达式,说明了每种技术:
1。从里到外替换:
<?php // test.php Rev:20121016_0900
$re = '% # Match innermost [b]...[/b] structure.
\[b\] # Literal start tag.
( # $1: Element contents.
# Use Friedls "Unrolling-the-Loop" technique:
# Begin: {normal* (special normal*)*} construct.
[^[]* # {normal*} Zero or more non-"[".
(?: # Begin {(special normal*)*}.
\[ # {special} Tag open literal char,
(?!/?b\]) # but only if NOT [b] or [/b].
[^[]* # More {normal*}.
)* # Finish {(special normal*)*}.
) # $1: Element contents.
\[/b\] # Literal end tag.
%x';
printf("Replace matching tags from the inside out:\n");
$text = file_get_contents('testdata.txt');
$i=0; // Keep track of iteration number.
printf("i[%d]=%s", $i++, $text);
while(preg_match($re, $text)){
$text = preg_replace($re, '<strong>$1</strong>', $text);
printf("i[%d]=%s", $i++, $text);
}
?>
输出:
'''
Replace matching tags from the inside out:
i[0]=Some text here... [b][b]Hello, [b]PHP![/b][/b][/b] ... [b]and here[/b]
i[1]=Some text here... [b][b]Hello, <strong>PHP!</strong>[/b][/b] ... <strong>and here</strong>
i[2]=Some text here... [b]<strong>Hello, <strong>PHP!</strong></strong>[/b] ... <strong>and here</strong>
i[3]=Some text here... <strong><strong>Hello, <strong>PHP!</strong></strong></strong> ... <strong>and here</strong>
'''
2。从外到内替换:
<?php // test.php Rev:20121016_0901
$re = '% # Match outermost [b]...[/b] structure.
\[b\] # Literal start tag.
( # $1: Element contents.
(?: # Zero or more contents alternatives.
[^[]* # Either non-[b]...[/b] stuff...
(?: # Begin {(special normal*)*}.
\[ # {special} Tag open literal char,
(?!/?b\]) # but only if NOT [b] or [/b].
[^[]* # More {normal*}.
)* # Finish {(special normal*)*}.
| (?R) # Or a nested [b]...[/b] structure.
)* # Zero or more contents alternatives.
) # $1: Element contents.
\[/b\] # Literal end tag.
%x';
printf("Replace matching tags from the outside in:\n");
$text = file_get_contents('testdata.txt');
$i=0; // Keep track of iteration number.
printf("i[%d]=%s", $i++, $text);
while(preg_match($re, $text)){
$text = preg_replace($re, '<strong>$1</strong>', $text);
printf("i[%d]=%s", $i++, $text);
}
?>
输出:
'''
Replace matching tags from the outside in:
i[0]=Some text here... [b][b]Hello, [b]PHP![/b][/b][/b] ... [b]and here[/b]
i[1]=Some text here... <strong>[b]Hello, [b]PHP![/b][/b]</strong> ... <strong>and here</strong>
i[2]=Some text here... <strong><strong>Hello, [b]PHP![/b]</strong></strong> ... <strong>and here</strong>
i[3]=Some text here... <strong><strong>Hello, <strong>PHP!</strong></strong></strong> ... <strong>and here</strong>
'''
请注意第二种方法中使用的 (?R)
递归表达式。
关于PHP,preg_replace 中的嵌套模板,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/12912165/