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Documentation Bug #13568. Added qualification for conditional function declarations.

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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@106123 c90b9560-bf6c-de11-be94-00142212c4b1
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Sara Golemon 2002-11-28 20:43:00 +00:00
parent ff2ece55ad
commit 2d81249fec
1 changed files with 72 additions and 2 deletions
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74
language/functions.xml
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@ -1,5 +1,5 @@
<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.28 $ -->
<!-- $Revision: 1.29 $ -->
<chapter id="functions">
<title>Functions</title>
@ -37,8 +37,78 @@ function foo ($arg_1, $arg_2, ..., $arg_n)
</simpara>
<simpara>
In PHP 3, functions must be defined before they are referenced. No
such requirement exists in PHP 4.
such requirement exists in PHP 4. <emphasis>Except</emphasis> when
a function is conditionally defined such as shown in the two examples
below.
</simpara>
<para>
When a function is defined in a conditional manner such as the two
examples shown. Its definition must be processed <emphasis>prior</emphasis>
to being called.
<example>
<title>Conditional functions</title>
<programlisting role="php">
<![CDATA[
<?php
$makefoo = true;
/* We can't call foo() from here
since it doesn't exist yet,
but we can call bar() */
bar();
if ($makefoo) {
function foo ()
{
echo "I don't exist until program execution reaches me.\n";
}
}
/* Now we can safely call foo()
since $makefoo evaluated to true */
if ($makefoo) foo();
function bar() {
{
echo "I exist immediately upon program start.\n";
}
?>
]]>
</programlisting>
</example>
<example>
<title>Functions within functions</title>
<programlisting role="php">
<![CDATA[
<?php
function foo()
{
function bar()
{
echo "I don't exist until foo() is called.\n";
}
}
/* We can't call bar() yet
since it doesn't exist. */
foo();
/* Now we can call bar(),
foo()'s processesing has
made it accessable. */
bar();
?>
]]>
</programlisting>
</example>
</para>
<simpara>
PHP does not support function overloading, nor is it possible to
undefine or redefine previously-declared functions.