Don't Fear the RegEx

Or how I learned to stop worrying and love the
[Rr]eg(ular)? ?[Ee]xp?(ression)?

Modifier	Definition
`i`	Make the complete pattern case insensitive
`m`	Treat each line as individual lines

Pattern	Will Match	Won't Match
a	a face	A b 3 ! foo
bart	bart Slartibartfast	Bart lisa 123
42	42 134237	1337 24 asdf
K-2SO	K-2SO	C-3PO R2-D2

Symbol	Character
`\t`	Tab
`\r`	Carriage Return
`\n`	Line Feed

Pattern	Will Match	Won't Match
.	a b C D 1 2 @ &	\r \n

Pattern	Will Match	Won't Match
[Ab3]	A b 3	a B 4
[0-9]	0 1 2 ... 9	a b C D
[a-z]	a b c ... z	A B C 1 2 3
[A-Z]	A B C ... Z	a b c 1 2 3
gr[ae]y	gray grey	groy

Pattern	Will Match	Won't Match
[^Abc]	a B C d E	A b c
[^0-9]	a b c	0 1 2 ... 9
[^Ff]ool	cool pool Tool	Fool fool

Pattern	Will Match	Won't Match
arthur\|ford\|zaphod	arthurfordzaphod	marvin
cat\|dog food	cat dog food	cat food
(cat\|dog) food	cat food dog food	hampster food

Pattern	Will Match	Won't Match
^art	art arthur	dart particle
art$	art dart	arthur particle
^art$	art	arthur dart particle

Pattern	Will Match	Won't Match
\bford	ford prefect fordoing	affordable oxford
ford\b	ford prefect oxford	affordable fordoing
\bford\b	ford ford prefect	affordable fordoing oxford

Symbol	Definition	Example
`\d`	Any decimal digit	[0-9]
`\h`	Any horizontal whitespace character	[ \t]*
`\s`	Any whitespace character	[ \t\r\n]
`\v`	Any vertical whitespace character	[\n\r]*
`\w`	Any (ASCII) "word" character	[A-Za-z0-9_]

Pattern	Will Match
vogons?	vogon vogons
colou?r	color colour

Pattern	Will Match	Wont Match
[A-Z][a-z]+	Arthur Ford	A F
[A-Z][a-z]*	Arthur Ford A F
0x[0-9A-F]+	0x2A 0x1092	0x 0x1Q7X

Pattern	Will Match	Wont Match
H{2}GT{2}G	HHGTTG	HGTG HHHGTTTG
No{1,3}!	No! Noo! Nooo!	N! Noooo!

Subject	Pattern	Result
`<strong>azPHP</strong>`	<.+>	<strong>azPHP</strong>
<.+?>	<strong>

Pattern	Will Match
([Hh]o ?){3}!	Ho ho ho!
(base\|foot)ball	baseball football

Pattern	Subject	Group	Content
([A-Za-z]+) ([A-Za-z]+)	`Arthur Dent`	0	Arthur Dent
1	Arthur
2	Dent

Pattern	Subject	Group	Content
(?:[A-Za-z]+) ([A-Za-z]+)	`Ford Prefect`	0	Ford Prefect
1	Prefect

Pattern	Subject	Group	Content
(?<first>[A-Za-z]+) (?<last>[A-Za-z]+)	`Zaphod Beeblebrox`	0	Zaphod Beeblebrox
first	Zaphod
last	Beeblebrox

Pattern	Will Match	Wont Match
<([a-z]+)>.+?<\/\1>	<strong>azPHP</strong> <small>NodeAZ</small>	<strong>azPHP</stronk>

Pattern	Will Match	Wont Match	Result
[Aa]rthur(?= [Dd]ent)	Arthur Dent	Arthur Prefect	`Arthur`
[Aa]rthur(?! [Dd]ent)	Arthur Prefect	Arthur Dent	`Arthur`
(?<=[Ff]ord )[Pp]refect	Ford Prefect	Arthur Prefect	`Prefect`
(?<![Ff]ord )[Pp]refect	Arthur Prefect	Ford Prefect	`Prefect`

preg_match( $pattern , $subject [, &$matches ] ): int

Searches $subject for a match to the regular expression given in $pattern.

If $matches is provided, then it is filled with the results of search.

Returns 1 if $pattern matchest given $subject, 0 if it does not.

$subject = "Sirius Cybernetics Corporation";

preg_match('/[Cc]([a-z]+)/', $subject, $matches); // 1

// $matches = [ "Cybernetics", "ybernetics" ]

preg_match_all( $pattern , $subject [, &$matches ] ): int

Searches $subject for all matches to the regular expression given in $pattern.

If $matches is provided, then it is filled with the results of search.

Returns the number of full pattern matches (could be 0).

$subject = 'How much wood would a woodchuck chuck if a woodchuck could chuck wood?';

preg_match_all('/wood([a-z]+)/', $subject, $matches); // 2

// $matches = [
//    [ "woodchuck", "woodchuck" ],
//    [ "chuck", "chuck" ],
// ]

preg_replace( $pattern , $replacement, $subject ): mixed

Searches $subject for matches to $pattern and replaces them with $replacement.

If matches are found, the new $subject will be returned,
otherwise $subject will be returned unchanged

preg_replace('/([Pp])ink/', '\1urple', 'John Pinkerton'); // John Purpleerton

preg_replace('/[^\d]/', null, '123-456-7890'); // 1234567890

preg_replace('#(\d{2})/(\d{2})/(\d{4})#', '\3-\1-\2', '05/20/1986'); // 1986-05-20

$pattern = ['/maroon/', '/gr[ae]y/', '/yellow|brown/'];
$replacement = ['red', 'silver', 'ugly'];

preg_replace($pattern, $replacement, 'The car was gray'); // The car was silver

preg_split( $pattern, $subject ): array

Split the given $subject by a string matched by $pattern.

preg_split('/[ .-]/', '1 123.456-7890'); // [ "1", "123", "456", "7890" ]

preg_quote( $str [, $delimiter ]): string

Escapes regular expression chracters from a string.

If $delimter is specified it will also be escaped.

Returns the escaped string.

preg_quote('[Foo]+Bar'); // \[Foo\]\+Bar

preg_quote('/path/to/file.txt', '/'); // \/path\/to\/file\.txt

URLs

www.google.com http://example.com/
https://regexr.com/5dubs https://www.azphp.org/#foobar https://api.example.net:1337/some/page?foo=bar&baz=qux ftp://user:password@fileserver.com

https://www.urlencoder.io/learn/

https://regexr.com/5ek37

Pick a format and match it (www.google.com)
[\w.~-]+
Capture the protocol (http, https, ftp, etc.)
([a-z]+:\/\/)?[\w.~-]+
Capture opional port and path (:1337/some/path)
([a-z]+:\/\/)?[\w.~-]+(:\d+)?(\/[\w\/.~-]*)?
Capture the query string and hash string
([a-z]+:\/\/)?[\w.~-]+(:\d+)?(\/[\w\/.~-]*)?(\?[\w=&.~-]*)?(#[\w.~-]*)?
And the username and password
([a-z]+:\/\/)?([\w]+(:.+)?@)?[\w.~-]+(:\d+)?(\/[\w\/.~-]*)?(\?[\w=&.~-]*)?(#[\w.~-]*)?

Don't Fear the RegEx Or how I learned to stop worrying and love the [Rr]eg(ular)? ?[Ee]xp?(ression)?

Don't Fear the RegEx

Chris Kankiewicz

Definition

Syntax

Delimiters

Modifiers

Patterns

Literal Text

Non-printable Characters

Meta Characters

Dot

Set

Negated Set

Alternation

Anchors

Word Boundry

Shorthand Character Classes

Quantifiers

Optional

Repitition

Specific Quantity

Greediness

Grouping

Groups

Capturing Groups

Non-capturing Groups

Named Groups

Back References

Lookarounds

Regular ExPHPressions

Perl-Compatible Regular Expression (PCRE)

Exercises

Phone Numbers

Time

URLs

https://regexcrossword.com

References