Regular Expressions 101

^start of line

Group 1(.+order_by=)

.+any character (except for line terminators), repeated at least once

order_by=the literal text order_by= (case sensitive)

.+?any character (except for line terminators), repeated at least once

Group 2(&|$)

1st Alternative&

&the literal & (38₁₀ / 46₈ / 26₁₆)

2nd Alternative$

$end of line

Group 3(.*)

.*any character (except for line terminators), repeated any number of times

$end of line

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.

Search reference

Regular Expression

^(.+order_by=).+?(&|$)(.*)$

New

http://www.stackoverflow.com?a=1&b=2
http://www.stackoverflow.com?a=2&b=3&order_by=old_data
http://www.stackoverflow.com?a=2&b=3&order_by=old_data&c=4
http://www.stackoverflow.com?order_by=old_data&a=2&b=3
http://www.stackoverflow.com

$1new_sort$2$3

Regular Expression

Substitution