& Functions

[Drezard]

I am currently reading the Zend Certification book. It talks about functions starting with a &. But, I dont quite understand what it means. When do you put a & at the front of a function?

 

The example it gives is:

 

function &query($sql)
{
$result = mysql_query($sql);
return $result;
}
// The following is incorrect and will cause PHP to emit a notice when called.
function &getHello()
{
return "Hello World";
}
// This will also cause the warning to be issued when called
function &test()
{
echo ’This is a test’;
}

 

Thanks, Daniel

[Daukan]

You can't use an & in front of a function. The & is used to call a variable by reference. It can be used with functions that return references.

<?php
$var1 = 'test';
$var2 =& $var;
function test_function($v) {
    if($v)
        return $v;
}
$var3 =& test_function($var2);
?>

A functions argument can reference a variable

<?php
$foo = 'test';
function change_var(&$var) {
    $var .= ' var';
}
change_var($foo);
echo $foo;// displays: test var
?>

[btherl]

Yes you can use & in front of a function.  But very few people do because it usually doesn't make sense.

 

The only situation I can think of when return by reference makes sense is when dealing with arrays.  The examples in Drezard's post, there seems to be no reason why you would return a mysql result be reference.