Regular Expressions 101

Explanation

Pro

<athe literal text <a (case sensitive)

Positive Lookahead(?=(?:(?!class="nothis")[^>])+>\s*<img)

Non-Capturing Group(?:(?!class="nothis")[^>])+

+repeats the group contents below at least once:

Negative Lookahead(?!class="nothis")

class="nothis"the literal text class="nothis" (case sensitive)

Negated Character Class[^>]

>the literal > (62₁₀ / 76₈ / 3E₁₆)

\s*any whitespace character, repeated any number of times

<imgthe literal text <img (case sensitive)

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

26 tokens

<a(?=(?:(?!class="nothis")[^>])+>\s*<img)

<a href="" class="nothis"><img src="" alt="" title="" border="0" /></a>
<a href="" class="yesthis"><img src="" alt="" title="" border="0" /></a>

<a href="" class="nothis"><img src="" alt="" title="" border="0" /></a>
<a href="" class="yesthis"><img src="" alt="" title="" border="0" /></a>