Get Error Message of the Last PCRE Regex Execution in PHP 8.0

The PCRE extension provides functions that allow to perform a regular expression (regex) matching operations. A regular expression is defined using the same syntax as Perl 5. This extension is included in PHP core.

A regular expression in PHP preg_ functions, such as preg_match, preg_replace, doesn't throw an exception if an error occurs during execution. Error can be manually inspected by using the preg_last_error function, which returns an error code.

<?php

preg_match('/(\D+)+[\d]/', 'hello hello hello hello');
echo preg_last_error();

Example will output 2. It means that backtrack limit was reached.

2

Since PHP 8.0, we can use a new preg_last_error_msg function which allows getting an error message of the last PCRE regular expression execution.

<?php

preg_match('/(\D+)+[\d]/', 'hello hello hello hello');
echo preg_last_error_msg();

Example will output:

Backtrack limit exhausted