The preg_last_error Function

The preg_last_error function returns the code of the last error, that occurred while working with regular expression functions. This is useful for debugging regular expressions when functions like preg_match or preg_replace return false. The function does not accept any parameters.

The function returns an integer error code. For convenience, the error code can be compared with special constants (see the table below).

Syntax

preg_last_error(): int;

Error Constants Table

Constant	Value	Description
`PREG_NO_ERROR`	0	No errors occurred
`PREG_INTERNAL_ERROR`	1	Internal PCRE error
`PREG_BACKTRACK_LIMIT_ERROR`	2	Backtrack limit was exhausted
`PREG_RECURSION_LIMIT_ERROR`	3	Recursion limit was exceeded
`PREG_BAD_UTF8_ERROR`	4	Malformed UTF-8 data
`PREG_BAD_UTF8_OFFSET_ERROR`	5	The offset did not correspond to the beginning of a valid UTF-8 code point
`PREG_JIT_STACKLIMIT_ERROR`	6	JIT stack limit was exceeded

Example

Let's check the error after an invalid regular expression:

<?php
	preg_match('/invalid(regex/', 'test');
	$error_code = preg_last_error();
	echo $error_code;
?>

Code execution result:

4

Example

Usage with PCRE error constants:

<?php
	preg_match('/(?:\D+/', 'abc123');
	if (preg_last_error() === PREG_BACKTRACK_LIMIT_ERROR) {
		echo 'Backtrack limit was exhausted';
	}
?>

Code execution result:

'Backtrack limit was exhausted'

The preg_last_error Function

Syntax

Error Constants Table

Example

Example

See Also