Regular Expressions 101

Explanation
Pro

Non-Capturing Group(?:\bextralistids\||(?<!^)\G)

1st Alternative\bextralistids\|

\ban ASCII word boundary

extralistidsthe literal text extralistids (case sensitive)

\|the literal | (124₁₀ / 174₈ / 7C₁₆)

2nd Alternative(?<!^)\G

Negative Lookbehind(?<!^)

^start of line

\Gstart of current search

Negated Character Class[^"]*

*matches any number of characters outside the set below:

"the literal " (34₁₀ / 42₈ / 22₁₆)

\"the literal " (34₁₀ / 42₈ / 22₁₆)

Group 1([^"\n]*)

Negated Character Class[^"\n]*

*matches any number of characters outside the set below:

"the literal " (34₁₀ / 42₈ / 22₁₆)

\na line-feed (newline) character (ASCII 10)

"the literal " (34₁₀ / 42₈ / 22₁₆)

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.

25 tokens

(?:\bextralistids\||(?<!^)\G)[^"]*\"([^"\n]*)"

extralistids|a:3:{i:0;s:3:"id1";i:1;s:4:" id2";i:2;s:4:" id3";}
extralistids|s:0:"";

extralistids|a:3:{i:0;s:3:"id1";i:1;s:4:" id2";i:2;s:4:" id3";}
extralistids|s:0:"";