= Regex Notation =

== Regex Quick Reference ==
^ Symbol       ^ Description ^
| [abc]        | A single character: a, b or c |
| [<nowiki>^</nowiki>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 |
| <nowiki>^</nowiki>            | Start of line |
| .            | 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 |
| (...)        | Capture everything enclosed |
| (a<nowiki>|</nowiki>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 |

General Tokens:
^ Symbol       ^ Description ^
| \n           | Newline |
| \r           | Carriage return |
| \t           | Tab |
| \f           | Form-feed |
| \0           | Null character |

Anchors:
^ Symbol       ^ Description ^
| \G           | Start of match |
| <nowiki>^</nowiki>            | Start of string |
| \A           | Start of string |
| $            | End of string |
| \Z           | End of string |
| \z           | Absolute end of string |
| \b           | Any word boundary character |
| \B           | Any non-word boundary |
| \w           | Any word character (letter, number, underscore) |
| \W           | Any non-word character |

Flags/Modifiers (eg: "/regex here.../g"):
^ Symbol       ^ Description  ^ 
| g  | Global (do not return after first match) |
| i  | Case insensitive |
| m  | Multiline (dot matches newlines, <nowiki>^</nowiki> and $ match start/end of line)  |
| s  | Single line (dot matches newline) |
| u  | Unicode (match with full unicode) | 
| x  | eXtended (ignore whitespace) | 
| X  | eXtra (disallow meaningless excapes| 
| o  | Perform #{...} substitutions only once |
| A  | Anchored (anchor to start of pattern) | 
| J  | Duplicate group names (allow duplicate subpattern names) | 
| D  | Dollar end only ($ matches only end of pattern) | 

== Using Regex in PHP ==

Can be used as ''ereg()'' or ''preg_match()''.  Here is a comparison:
<code php>
<?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. 
?>
</code>

Using options:
<code php>
<?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.";
}
?>
</code>

Example using ''preg_replace()'':
<code php>
// Strip ending commas
$str = preg_replace('/,$/s', '', $str);

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

== References ==
  * [[http://www.rexegg.com/regex-quickstart.html|Regex Cheat Sheet]]
  * [[https://regex101.com|Regex 101]]