Regular Expressions (Perl-Compatible)

Introduction

This extension integrates regular expression pattern matching support into PHP. It is based on the free and open-source » PCRE2 library. This library implements regular expression pattern matching using syntax and semantics compatible with Perl, with a few » documented differences. See Pattern Syntax and Pattern Modifiers for a detailed explanation.

To improve performance, the extension caches compiled regular expressions. Each thread has its own dedicated cache, capable of holding up to 4096 expressions.

Note:
When the cache is full, a batch of the oldest entries that are not currently in use is discarded to make room for new ones. The cache size is not configurable.

Warning

PCRE2 imposes » size and other limits that may be relevant in some cases.

Installing/Configuring
- Installation
- Runtime Configuration
Predefined Constants
Examples
PCRE Patterns
- PCRE regex syntax — Pattern Syntax
- Possible modifiers in regex patterns — Pattern Modifiers
- Differences From Perl — Perl Differences
PCRE Functions
- preg_filter — Perform a regular expression search and replace
- preg_grep — Return array entries that match the pattern
- preg_last_error — Returns the error code of the last PCRE regex execution
- preg_last_error_msg — Returns the error message of the last PCRE regex execution
- preg_match — Perform a regular expression match
- preg_match_all — Perform a global regular expression match
- preg_quote — Quote regular expression characters
- preg_replace — Perform a regular expression search and replace
- preg_replace_callback — Perform a regular expression search and replace using a callback
- preg_replace_callback_array — Perform a regular expression search and replace using callbacks
- preg_split — Split string by a regular expression