Regular Expression functions allow you to search specific patterns in the string and replace them with some other pattern/string.

On this page, you will find the regular expression functions, their relative information like special characters/symbols, and their meanings.

FunctionDescription
preg_filter()Get string or array with pattern matches replaced, but only if matches were found
preg_grep()Get an array of elements from the input array which matched the pattern
preg_last_error()Get an error code showing the reason that the last regular expression call failed
preg_match()Get the first match of a pattern in a string
preg_match_all()Get all matches of a pattern in a string
preg_replace()Get strings were matches of a pattern replaced with a substring. The substring value is returned by the callback function.
preg_replace_callback()Get string where all matches of the expression are replaced with the substring. The substring value is returned by the callback function.
preg_replace_callback_array()Get a string where all matches of each expression are replaced with the substring. The substring value is returned by the callback function.
preg_split()Break the string based on the regular expressions and return the partitions of the string as array
preg_quote()Put a backslash in front of characters that have a special meaning in regular expressions
PHP Regex Functions

Modifiers in Regex

Modifiers define the behavior of searching for patterns in the string.

ModifierDescription
icase-insensitive search for the pattern
mSearch in multiline. That is, search for a matching pattern at the beginning or end of each line
uEnables correct matching of UTF-8 encoded patterns
Expression Modifiers

Regex Patterns

Brackets define the range of characters to create patterns.

[abc]Find a character from the items between the brackets
[^abc]Find character NOT between the brackets
[0-9]Find a character from 0 to 9
Regular Expression Patterns

Regex Metacharacters

Metacharacters are characters with a special meaning:

MetacharacterDescription
|Look for a match for any one of the patterns separated by |
.Look for one instance of any character
^Look for a match as the beginning of a string
$Find match at the end of the string
\dFind a digit
\sFind a whitespace character
\bFind a match at the beginning of a word
\uxxxxFind the Unicode character given by the hexadecimal number XXXX
Metacharacters in PHP regex

Quantifiers in Regex

Quantities are defined by quantifiers.

QuantifierDescription
n+Find string containing at least one n
n* Find string containing zero or more occurrences of n
n? Find string containing zero or one occurrence of n
n{x} Find string containing sequence of X n‘s
n{x,y} Find string containing sequence of X to Y n‘s
n{x,} Find string containing sequence of at least X n‘s
Quantifiers