&reftitle.constants; &extension.constants;

# PREG constants

&Constants; | &Description; | As of
`PREG_PATTERN_ORDER` (`int`) | Orders results so that `$matches[0]` is an array of full pattern matches, `$matches[1]` is an array of strings matched by the first parenthesized subpattern, and so on. This flag is only used with `preg_match_all`. |
`PREG_SET_ORDER` (`int`) | Orders results so that `$matches[0]` is an array of first set of matches, `$matches[1]` is an array of second set of matches, and so on. This flag is only used with `preg_match_all`. |
`PREG_OFFSET_CAPTURE` (`int`) | See the description of `PREG_SPLIT_OFFSET_CAPTURE`. |
`PREG_SPLIT_NO_EMPTY` (`int`) | This flag tells `preg_split` to return only non-empty pieces. |
`PREG_SPLIT_DELIM_CAPTURE` (`int`) | This flag tells `preg_split` to capture parenthesized expression in the delimiter pattern as well. |
`PREG_SPLIT_OFFSET_CAPTURE` (`int`) | If this flag is set, for every occurring match the appendant string offset will also be returned. Note that this changes the return values in an array where every element is an array consisting of the matched string at offset 0 and its string offset within subject at offset 1. This flag is only used for `preg_split`. |
`PREG_UNMATCHED_AS_NULL` (`int`) | This flag tells `preg_match` and `preg_match_all` to include unmatched subpatterns in `$matches` as &null; values. Without this flag, unmatched subpatterns are reported as empty strings, as if they were empty matches. Setting this flag allows to distinguish between these two cases. | 7.2.0
`PREG_NO_ERROR` (`int`) | Returned by `preg_last_error` if there were no errors. | 5.2.0
`PREG_INTERNAL_ERROR` (`int`) | Returned by `preg_last_error` if there was an internal PCRE error. | 5.2.0
`PREG_BACKTRACK_LIMIT_ERROR` (`int`) | Returned by `preg_last_error` if backtrack limit was exhausted. | 5.2.0
`PREG_RECURSION_LIMIT_ERROR` (`int`) | Returned by `preg_last_error` if recursion limit was exhausted. | 5.2.0
`PREG_BAD_UTF8_ERROR` (`int`) | Returned by `preg_last_error` if the last error was caused by malformed UTF-8 data (only when running a regex in UTF-8 mode). | 5.2.0
`PREG_BAD_UTF8_OFFSET_ERROR` (`int`) | Returned by `preg_last_error` if the offset didn't correspond to the begin of a valid UTF-8 code point (only when running a regex in UTF-8 mode). | 5.3.0
`PREG_JIT_STACKLIMIT_ERROR` (`int`) | Returned by `preg_last_error` if the last PCRE function failed due to limited JIT stack space. | 7.0.0
`PCRE_VERSION` (`string`) | PCRE version and release date (e.g. "`7.0 18-Dec-2006`"). | 5.2.4