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Doc Bug #18480 Undocumented global use
Submitted: 2002-07-22 18:47 UTC Modified: 2002-07-23 10:44 UTC
From: seb at delahaye dot net Assigned:
Status: Closed Package: Documentation problem
PHP Version: 4.2.1 OS: all
Private report: No CVE-ID: None
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From: seb at delahaye dot net
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 [2002-07-22 18:47 UTC] seb at delahaye dot net 
One of the uses of "global $var;" seems not to be documented. Here's a tiny patch to fix that.

--beginning--
Index: en/language/variables.xml
===================================================================
RCS file: /repository/phpdoc/en/language/variables.xml,v
retrieving revision 1.52
diff -u -u -r1.52 variables.xml
--- en/language/variables.xml	3 Jul 2002 22:51:23 -0000	1.52
+++ en/language/variables.xml	22 Jul 2002 22:34:16 -0000
@@ -380,6 +380,47 @@
    </simpara>
 
    <simpara>
+    Please note that if you want to access in your function to a variable
+    which is in another function, all that through a global variable,
+    you'll need to declare it as a variable in the two functions.
+    An example, always with our function Sum():
+   </simpara>
+
+   <informalexample>
+    <programlisting role="php">
+<![CDATA[
+<?php
+
+function KeepVariables()
+{
+    global $a, $b;
+
+    $a = 1;
+    $b = 2;
+}
+
+function Sum()
+{
+    global $a, $b;
+
+    $b = $a + $b;
+} 
+
+KeepVariables();
+Sum();
+echo $b;
+?>
+]]>
+    </programlisting>
+   </informalexample>
+
+   <simpara>
+    If we hadn't declared <varname>$a</varname> and <varname>$b</vargame>
+    as globals in the KeepVariables() function, the script would have
+    displayed nothing.
+   </simpara>
+
+   <simpara>
     A second way to access variables from the global scope is to use
     the special PHP-defined <varname>$GLOBALS</varname> array.  The
     previous example can be rewritten as:

--end--

If it can be useful, I can also write a french version of it, since I'm french.

HTH.

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 [2002-07-22 18:54 UTC] rasmus@php.net 
That's not a different use though.  You are simply creating a global variable in one function and accessing it in another.  I don't think this patch clarifies anything.  Perhaps the fact that you can create global variables inside a function is not documented well enough, but a much simpler documentation fix can take care of that.
 [2002-07-22 19:00 UTC] seb at delahaye dot net 
For me, the fact that it was needed to create a global variable in one function to access to in another was not clear. Specially because it's not the case for vars that are outside any function. I don't think it's something evident.

My patch probably doesn't explain it well, I'll try to make one more clear tomorrow (yup, it's damn too late here).
 [2002-07-22 19:05 UTC] rasmus@php.net 
I really don't understand why this point would have confused you.  The only variables you can access inside a function are the variables local to that specific function.  If you want to access a variable defined outside of the function (ie. a global) you have to specify you want to access that global variable.  There is no way for a function to access another function's locally scoped variables.
 [2002-07-23 10:27 UTC] seb at delahaye dot net 
Yes. I knew I had to declare the var as global is the function where I wanted to use it. What was not clear for me was that I  needed to declare it as global in the two functions. If I take the functions from the patch as example, declaring $a and $b as global in Sum() was evident, but declaring them as global also in KeepVariables() was not evident.

Of course, when you *know* it, it's clear, but when you don't know it, and since the doc isn't IMHO clear about this, it's not evident at all.

This patch should be more clear (hopefully):

Index: en/language/variables.xml
===================================================================
RCS file: /repository/phpdoc/en/language/variables.xml,v
retrieving revision 1.52
diff -u -r1.52 variables.xml
--- en/language/variables.xml	3 Jul 2002 22:51:23 -0000	1.52
+++ en/language/variables.xml	23 Jul 2002 14:26:36 -0000
@@ -375,8 +375,10 @@
     The above script will output &quot;3&quot;.  By declaring
     <varname>$a</varname> and <varname>$b</varname> global within the
     function, all references to either variable will refer to the
-    global version.  There is no limit to the number of global
-    variables that can be manipulated by a function.
+    global version. In the same way, if you want to access in a function
+    to a var from another function, declare it as global in both functions.
+    There is no limit to the number of global variables that can be
+    manipulated by a function.
    </simpara>
 
    <simpara>
 [2002-07-23 10:40 UTC] cynic@php.net 
gosh, and how would the KeepVariables() function know to access the *global* variables $a and $b if you didn't tell it to?

this is IMO just a matter of common sense, so please, stop this thread.
 
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