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Add more explanations, small fixes

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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@30582 c90b9560-bf6c-de11-be94-00142212c4b1
This commit is contained in:
Stanislav Malyshev 2000-08-20 10:28:13 +00:00
parent 987c42587c
commit 4a2d9feae9
1 changed files with 43 additions and 35 deletions
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78
language/references.xml
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@ -21,8 +21,7 @@
<informalexample>
<programlisting role="php">
$a =&amp; $b
</programlisting>
$a =&amp; $b </programlisting>
</informalexample>
it means that <varname>$a</varname> and <varname>$b</varname> point to
@ -38,23 +37,27 @@ $a =&amp; $b
</para>
<para>
The second thing references do is to pass variables by-references. This is
The second thing references do is to pass variables by-reference. This is
done by making local function variable and caller variable to be reference
to the same content. Example:
<informalexample>
<programlisting role="php">
function foo(&amp;$var) {
$var++;
}
function foo(&amp;$var) {
$var++;
}
$a=5;
foo($a);
</programlisting>
$a=5;
foo($a);</programlisting>
</informalexample>
will make <varname>$a</varname> to be 6.
will make <varname>$a</varname> to be 6. This happens because in the function <varname>foo</varname> the variable <varname>$var</varname> refers to the same content as <varname>$a</varname>.
</para>
<simpara>
The third thing reference can do is
<link linkend="language.references.return">return by-reference</link>.
</simpara>
</sect1>
<sect1 id="language.references.arent">
@ -65,22 +68,22 @@ foo($a);
<informalexample>
<programlisting role="php">
function foo(&amp;$var) {
$var =&amp; $GLOBALS["baz"];
}
foo($bar);
</programlisting>
function foo(&amp;$var) {
$var =&amp; $GLOBALS["baz"];
}
foo($bar); </programlisting>
</informalexample>
</para>
<simpara>
What will happen that <varname>$var</varname> in foo will be bound with
<varname>$bar</varname> in caller, but then it will be re-bound with
<varname>$GLOBALS["baz"]</varname>. There's no way to bind <varname>$bar</varname>
in caller to something else using reference mechanism, since
<varname>$bar</varname> is not available in the function foo (it is
represented by <varname>$var</varname>, but <varname>$var</varname>
has only variable contents and not name-to-value binding).
<varname>$GLOBALS["baz"]</varname>. There's no way to bind
<varname>$bar</varname> in the caller to something else using reference
mechanism, since <varname>$bar</varname> is not available in the function
foo (it is represented by <varname>$var</varname>, but
<varname>$var</varname> has only variable contents and not name-to-value
binding in the calling symbol table).
</simpara>
</sect1>
@ -93,18 +96,25 @@ foo($bar);
<informalexample>
<programlisting role="php">
function &amp;find_var($param) {
...code...
return $found_var;
}
function &amp;find_var($param) {
...code...
return $found_var;
}
$foo =&amp; find_var($bar);
</programlisting>
$foo =&amp; find_var($bar);
$foo->x = 2; </programlisting>
</informalexample>
In this example, property of the object returned by the
<varname>find_var</varname> function would be set, not of the copy, as
it would be without using reference syntax.
</para>
<note>
<simpara>
Unlike parameter passing, here you use &amp; in both places.
Unlike parameter passing, here you have to use <literal>&amp;</literal>
in both places - to indicate that you return by-reference, not a copy
as usual, and to indicate than reference binding and not usual
assignment should be done for <varname>$foo</varname>.
</simpara>
</note>
</sect1>
@ -118,19 +128,17 @@ $foo =&amp; find_var($bar);
<informalexample>
<programlisting role="php">
$a = 1;
$b =&amp; $a;
unset($a);
</programlisting>
$a = 1;
$b =&amp; $a;
unset($a); </programlisting>
</informalexample>
won't unset <varname>$b</varname>, just <varname>$a</varname>.
</para>
<simpara>
Again, it might be useful to think about this as analogous to Unix unlink
call.
Again, it might be useful to think about this as analogous to Unix
<command>unlink</command> call.
</simpara>
</sect1>
@ -154,7 +162,7 @@ unset($a);
<informalexample>
<programlisting role="php">
$var =&amp; $GLOBALS["var"];</programlisting>
$var =&amp; $GLOBALS["var"];</programlisting>
</informalexample>
</para>