== Why is this an issue?

While PHP variables obligingly spring into existence the first time you use them, relying on this behavior is a bad idea for two reasons. First, relying on the default value of an uninitialized variable can cause problems in some cases. Second, and more importantly, it can pose a security risk when ``++register_globals++`` is enabled. (Note that ``++register_globals++`` is deprecated in PHP 5.3 and removed in PHP 5.4.)


=== Noncompliant code example

[source,php]
----
$a = $b + 4;  // Noncompliant; this initializes $a, but $b is uninitialized

if (authenticated($user)) {
  $authorized = true;  // Noncompliant. What value does $authorized have if the user is not authenticated?
}
----


=== Compliant solution

[source,php]
----
$b = doSomething();
$a = $b + 4;

$authorized = false;
if (authenticated($user)) {
  $authorized = true;
}
----


== Resources

* CWE - https://cwe.mitre.org/data/definitions/457[CWE-457 - Use of Uninitialized Variable]


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

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

=== Message

* Initialize "xx" before this usage.
* Use "isset()" to make sure "xx" is initialized before this usage.


'''
== Comments And Links
(visible only on this page)

=== is related to: S2669

=== on 19 Sep 2014, 15:35:43 Freddy Mallet wrote:
@Ann, if my feeling is correct, this rule relates to \http://cwe.mitre.org/data/definitions/457.html and in that case we can also target C and {cpp}

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