preg_match_all提取字符串部分的最佳模式是什么？

Question

Context ;

• from file_get_contents from url, i get lots of stuff like <item></item>, <url></url>, etc.

• i'm using preg_match_all to extract url, title, etc.

example:

$jStringToSubStract = '<a>stuffA</a><b>stuffB</b><url>http...</url>';
preg_match_all("#<url>(.*?)<\/url>#sx", $jStringToSubStract , $subItems, PREG_SET_ORDER);
foreach ( $subItems as $subItem  ) {        
        if ( strlen ($subItem[1]) > 0 ) {
            echo $subItem[1]; // this is returning the http... INSIDE <url></url> 
        }
}

but it's slow for a large amount...

Is there a faster alternative to preg_match_all to extract portion of strings ?

Answer 1

After seeing your posted solution, I now understand what you are trying to achieve. Since you are capturing only substrings in the format of [attrname]=[attrvalue] (which may be single quoted, double quoted, or not quoted at all), these are optimized patterns for you...

This one will get ALL attributes: \K\S+=["']?[^>"']+["']?>?? Demo

This one will get specific attributes: \K(?:alt|title|src|href)=["']?[^>"']+["']?>?? Demo

These patterns do not use capture groups. This means your code will avoid unnecessary result array bloat and access the substrings as fullstring matches. Both of these patterns will run more efficiently than the patterns you have posted.

I should also mention that both my patterns and your patterns are not 100% reliable because there is no check that these substrings are actually inside of html tags. This is the reason why html-parsing programs are strenuously encouraged. If you are certain that the text that you'll be reading won't have any free floating \S=\S formatted strings outside of the tags, then the results will be fine.