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