rspec/rules/S6328/php/rule.adoc

The PHP function ``++preg_replace++`` can be used to perform a search and replace based on regular expression matches. The ``++$replacement++`` parameter can contain references to capturing groups used in the ``++$pattern++`` parameter. This can be achieved with ``++\n++`` or ``++$n++`` to reference the n'th group. 

When referencing a nonexistent group, it will be substituted with an empty string. This is in general not the intended behavior, and might stay unnoticed since no warning is raised. 

== Noncompliant Code Example

[source,php]
----
preg_replace("/(a)(b)(c)/", "\\1, \\9, \\3", "abc"); // Noncompliant - result is "a, , c"
----

== Compliant Solution

[source,php]
----
preg_replace("/(a)(b)(c)/", "\\1, \\2, \\3", "abc");
----

== See

* https://www.php.net/manual/en/function.preg-replace.php[preg_replace] - PHP Documentation

ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

== Message

Make sure to reference an existing group.

== Highlighting

The reference to the group that does not exist.

'''

endif::env-github,rspecator-view[]