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.
| Function | Description |
|---|---|
| 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 |
Modifiers in Regex
Modifiers define the behavior of searching for patterns in the string.
| Modifier | Description |
|---|---|
| i | case-insensitive search for the pattern |
| m | Search in multiline. That is, search for a matching pattern at the beginning or end of each line |
| u | Enables correct matching of UTF-8 encoded patterns |
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 |
Regex Metacharacters
Metacharacters are characters with a special meaning:
| Metacharacter | Description |
|---|---|
| | | 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 |
| \d | Find a digit |
| \s | Find a whitespace character |
| \b | Find a match at the beginning of a word |
| \uxxxx | Find the Unicode character given by the hexadecimal number XXXX |
Quantifiers in Regex
Quantities are defined by quantifiers.
| Quantifier | Description |
|---|---|
| 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 |
