system:regex:regex_notation [Audina Documentation]

This is an old revision of the document!

Regex Notation

Regex Quick Reference

Symbol	Description
[abc]	A single character: a, b or c
[^abc]	Any single character but a, b, or c
[a-z]	Any single character in the range a-z
[a-zA-Z]	Any single character in the range a-z or A-Z
^	Start of line
$	End of line
\A	Start of string
\z	End of string
.	Any single character
\s	Any whitespace character
\S	Any non-whitespace character
\d	Any digit
\D	Any non-digit
\w	Any word character (letter, number, underscore)
\W	Any non-word character
\b	Any word boundary character
(…)	Capture everything enclosed
(a\|b)	a or b
a?	Zero or one of a
a*	Zero or more of a
a+	One or more of a
a{3}	Exactly 3 of a
a{3,}	3 or more of a
a{3,6}	Between 3 and 6 of a

Options:

i	Case insensitive
m	Make dot match newlines
x	Ignore whitespace in regex
o	Perform #{…} substitutions only once

Using Regex in PHP

Can be used as ereg() or preg_match(). Here is a comparison:

<?php 
if(ereg('[^0-9A-Za-z]',$test_string)) // will be true if characters arnt 0-9, A-Z or a-z. 
 
if(preg_match('/[^0-9A-Za-z]/',$test_string)) // this is the preg_match version. the /'s are now required. 
?>

Using options:

<?php
// The "i" after the pattern delimiter indicates a case-insensitive search
if (preg_match("/php/i", "PHP is the web scripting language of choice.")) {
    echo "A match was found.";
} else {
    echo "A match was not found.";
}
?>

Example using preg_replace():

// Strip leading/trailing commas with whitespace around
$str = preg_replace('/^[,\s]+|[\s,]+$/', '', $str);