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POWhat does `protected` mean in PHP?
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2013-10-21T13:53:30.300
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I was reading through some PHP code, and I noticed a class calling a protected method on its sibling (inherited from a common parent). This strikes me as counter-intuitive. Does <code>in the same inheritance tree</code> in PHP mean something <a href="https://stackoverflow.com/a/215505/12570">like Java's <code>part of the same package</code></a> ? <a href="http://msdn.microsoft.com/en-us/library/ba0a1yw2.aspx" rel="nofollow noreferrer">I'm more used to the C# meaning of <code>protected</code>.</a> Because I am more used to C#'s meaning of protected, I was not expecting to be able to call the protected method on a sibling class. In Java, the distinction is clear from the package. Is there anything, other than inheritance, that defines accessibility in this instance in PHP? <pre><code><? class C1 { protected function f() { echo "c1\n"; } } class C2 extends C1 { protected function f() { echo "c2\n"; } } class C3 extends C1 { public function f() { // Calling protected method on parent. $c1 = new C1(); $c1 -> f(); // Calling protected method on sibling??!? $c2 = new C2(); $c2 -> f(); echo "c3\n"; } } $c3 = new C3(); $c3 -> f(); // OUTPUT: // c1 // c2 // c3 </code></pre> Here's me trying to the same thing in C# (and failing). <pre><code>using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication2 { class c1 { protected void f() { Console.WriteLine("c1"); } } class c2: c1 { protected void f() { Console.WriteLine("c2"); } public void g() { Console.WriteLine("g!"); } } class c3 : c1 { protected void f() { // Error 1 Cannot access protected member 'ConsoleApplication2.c1.f()' // via a qualifier of type 'ConsoleApplication2.c1'; the qualifier must be // of type 'ConsoleApplication2.c3' (or derived from it) //c1 cone = new c1(); //cone.f(); base.f(); c2 ctwo = new c2(); //Error 1 'ConsoleApplication2.c2.f()' is inaccessible due to its protection level ctwo.f(); ctwo.g(); Console.WriteLine("c3"); } } class Program { static void Main(string[] args) { c3 cthree = new c3(); // Error 2 'ConsoleApplication2.c3.f()' is inaccessible due to its protection level cthree.f(); } } } </code></pre> <hr> It looks like the behaviour expected was the case prior to PHP 5.2. <a href="https://wiki.php.net/rfc/protectedlookup" rel="nofollow noreferrer">This RFC explains the issue a little more</a>, and points to <a href="https://bugs.php.net/bug.php?id=37632" rel="nofollow noreferrer">why the change happened in this bug</a>. I'm not sure it quite answers my question, but I thought I'd update the question, in case it helps anyone. Thanks to Robin F., for <a href="http://marc.info/?t=120221202200001&r=1&w=2" rel="nofollow noreferrer">pointing me to this discussion of the RFC</a>, for some background.
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<php><inheritance><siblings>
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What does `protected` mean in PHP?
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