php preg_match_all的解释

Question

我是新来的PHP和困惑的preg_match_all（）函数。

有人可以解释什么功能的每个部分在这个例子中做？

preg_match_all("/<item><title>([^<]*) - ([^<]*?)<\/title>/i", $buffer, $titlematches); 

Answer 1

这是一个正则表达式，它们是棘手的混蛋，直到你习惯生活在其中。它们不仅适用于PHP，每种语言都具有使用它们的功能。

这是搜索$buffer，在<item>元素内寻找<title>元素。它正在寻找<title>元素中的两个由-分隔的文本块（第二个块是可选的）。找到的文本块保存到$titlematches以供在脚本中使用。

正如在其他答案中提到的，http://regex101.com/是一个很好的资源来检查你的语法，但可能不适合初学者！

Answer 2

/([^<]) - ([^<]?)<\/title>/i 
1st Capturing group ([^<]) 
[^<] match a single character not present in the list below 
< a single character in the list < literally (case insensitive) 
- matches the characters - literally 
2nd Capturing group ([^<]?) 
[^<]? match a single character not present in the list below 
Quantifier: ? Between zero and one time, as many times as possible, giving back as needed [greedy] 
< a single character in the list < literally (case insensitive) 
< matches the characters < literally 
\/ matches the character/literally 
title> matches the characters title> literally (case insensitive) 
i modifier: insensitive. Case insensitive match (ignores case of [a-zA-Z]) 

https://regex101.com/