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在尝试匹配 xml 文档中的单个第一个节点时，使用正则表达式

~<(\S+).*>.*</\1>~, 在文本达到一定长度之前，它什么都不匹配。在一个文档中，当我将文本剥离到 ​​1186 个字符后，正则表达式成功地找到了一些东西。在下面的示例中，我剥离了文本，直到它只有 960 个字符，然后正则表达式成功。可以想象，这种看似不一致的行为非常令人困惑。我将不胜感激有关为什么会发生这种情况的任何信息。

原文：

<?xml version="1.0"?> <catalog> <book id="bk101"> <author>Gambardella, Matthew</author> <title>XML Developer's Guide</title> <genre>Computer</genre> <price>44.95</price> <publish_date>2000-10-01</publish_date> <description>An in-depth look at creating applications with XML.</description> </book> <book id="bk102"> <author>Ralls, Kim</author> <title>Midnight Rain</title> <genre>Fantasy</genre> <price>5.95</price> <publish_date>2000-12-16</publish_date> <description>A former architect battles corporate zombies, an evil sorceress, and her own childhood to become queen of the world.</description> </book> <book id="bk103"> <author>Corets, Eva</author> <title>Maeve Ascendant</title> <genre>Fantasy</genre> <price>5.95</price> <publish_date>2000-11-17</publish_date> <description>After the collapse of a nanotechnology society in England, the young survivors lay the foundation for a new society.</description> </book> <book id="bk104"> <author>Corets, Eva</author> <title>Oberon's Legacy</title> <genre>Fantasy</genre> <price>5.95</price> <publish_date>2001-03-10</publish_date> <description>In post-apocalypse England, the mysterious agent known only as Oberon helps to create a new life for the inhabitants of London. Sequel to Maeve Ascendant.</description> </book> <book id="bk105"> <author>Corets, Eva</author> <title>The Sundered Grail</title> <genre>Fantasy</genre> <price>5.95</price> <publish_date>2001-09-10</publish_date> <description>The two daughters of Maeve, half-sisters, battle one another for control of England. Sequel to Oberon's Legacy.</description> </book> <book id="bk106"> <author>Randall, Cynthia</author> <title>Lover Birds</title> <genre>Romance</genre> <price>4.95</price> <publish_date>2000-09-02</publish_date> <description>When Carla meets Paul at an ornithology conference, tempers fly as feathers get ruffled.</description> </book> <book id="bk107"> <author>Thurman, Paula</author> <title>Splish Splash</title> <genre>Romance</genre> <price>4.95</price> <publish_date>2000-11-02</publish_date> <description>A deep sea diver finds true love twenty thousand leagues beneath the sea.</description> </book> <book id="bk108"> <author>Knorr, Stefan</author> <title>Creepy Crawlies</title> <genre>Horror</genre> <price>4.95</price> <publish_date>2000-12-06</publish_date> <description>An anthology of horror stories about roaches, centipedes, scorpions and other insects.</description> </book> <book id="bk109"> <author>Kress, Peter</author> <title>Paradox Lost</title> <genre>Science Fiction</genre> <price>6.95</price> <publish_date>2000-11-02</publish_date> <description>After an inadvertant trip through a Heisenberg Uncertainty Device, James Salway discovers the problems of being quantum.</description> </book> <book id="bk110"> <author>O'Brien, Tim</author> <title>Microsoft .NET: The Programming Bible</title> <genre>Computer</genre> <price>36.95</price> <publish_date>2000-12-09</publish_date> <description>Microsoft's .NET initiative is explored in detail in this deep programmer's reference.</description> </book> <book id="bk111"> <author>O'Brien, Tim</author> <title>MSXML3: A Comprehensive Guide</title> <genre>Computer</genre> <price>36.95</price> <publish_date>2000-12-01</publish_date> <description>The Microsoft MSXML3 parser is covered in detail, with attention to XML DOM interfaces, XSLT processing, SAX and more.</description> </book> <book id="bk112"> <author>Galos, Mike</author> <title>Visual Studio 7: A Comprehensive Guide</title> <genre>Computer</genre> <price>49.95</price> <publish_date>2001-04-16</publish_date> <description>Microsoft Visual Studio 7 is explored in depth, looking at how Visual Basic, Visual C++, C#, and ASP+ are integrated into a comprehensive development environment.</description> </book> </catalog>

修剪（成功）的文本：

<?xml version="1.0"?> <catalog> <book id="bk101"> <author>Gambardella, Matthew</author> <title>XML Developer's Guide</title> <genre>Computer</genre> <price>44.95</price> <publish_date>2000-10-01</publish_date> <description>An in-depth look at creating applications with XML.</description> </book> <book id="bk102"> <author>Ralls, Kim</author> <title>Midnight Rain</title> <genre>Fantasy</genre> <price>5.95</price> <publish_date>2000-12-16</publish_date> <description>A former architect battles corporate zombies, an evil sorceress, and her own childhood to become queen of the world.</description> </book> <book id="bk103"> <author>Corets, Eva</author> <title>Maeve Ascendant</title> <genre>Fantasy</genre> <price>5.95</price> <publish_date>2000-11-17</publish_date> <description>After the collapse of a nanotechnology society in England, the young survivors lay the foundation for a new society.</description> </book> <book id="bk104"> <author>Core</catalog>

对于文本的格式，我深表歉意，但我不想在数据中添加某些内容以使其对其他人的行为有所不同（例如换行符）。

编辑：我一直在使用这个网站测试正则表达式。

4

3 回答 3

2

该函数preg_match() 具有 - 类似于许多其他 PHP 函数 - 一个返回值。

根据该返回值是什么，您可以决定脚本应该如何进行。

在您的情况下，您实际上没有检查返回值是FALSE. 因为 - 正如您的示例所示，它是FALSE.

阅读手册表明返回值FALSE表示错误。preg_last_error()您可以通过调用给出最后一个错误代码的函数来了解有关该错误的更多信息。因此，您可以了解您调用的preg_match()错误：

int(2) - PREG_BACKTRACK_LIMIT_ERROR

另见：

于 2013-07-15T17:38:45.070 回答
1

您可以使用约束字符类更好地控制量词：

带有惰性量词的示例：

$pattern = '~<([^>\s]++)[^>]*+>.*?</\1>~';

仅使用所有格量词的示例（更好）：

$pattern = '~<([^>\s]++)[^>]*+>(?>[^<]++|<(?!/\1>))+</\1>~';

但这两种模式不处理嵌套结构，为此您必须使用：

$pattern = '~<([^>/\s]++)[^>]*+>(?>[^<]++|(?R))*</\1>~';


细节：

第二种模式：(?>[^<]++|<(?!/\1>))+

(?>           # open an atomic group
   [^<]++     # all characters but < one or more times (possessive)
  |           # OR
   <(?!/\1)   # < not followed by / and the content of the first backreference
              #  (the tag name here)
)+            # close the atomic group and repeat one or more times

这样做的目标是匹配所有直到</\1>，这个想法是匹配所有不是 a<或所有<不跟随的/tagname>

有关所有格量词和原子组的更多信息。


第三种模式：递归模式 

<                                
  ([^>/\s]++)     # tagname, 
                  # note that you must exclude the / to avoid closing tags
  [^>]*+          # leading characters in the tag
>


(?>               # open an atomic group
   [^<]++         # all characters but <, one or more times (possessive)
  |               # OR
   (?R)           # repeat the whole pattern
)*                # close the atomic group, repeat zero or more times

</\1>             # close tag with the first back reference
于 2013-07-15T17:28:59.607 回答
-1

嗯，首先 - 一般的态度是不应该用 RegEx 解析 XML。如果可能，请改用 SimpleXML。正如nickb所说，太贪婪了......

于 2013-07-15T17:10:38.213 回答