PHP Returned Links
Return by reference is useful when you want to use a function to find which variable should be referenced . Don't use a backlink to improve performance. The engine will automatically optimize this for its own. Only return links when you have a valid technical reason to do so.
What does bold mean?
does this mean something like
public function & getHellos () {
$ sql = 'SELECT id, greeting FROM #__hello';
$ data = $ this -> _ getList ($ sql);
return $ data;
}
where am i not bound to any variable?
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We return by reference when we want the function to GetRef()
determine which variable $foo
or $bar
reference $foo_or_bar
should be linked:
$foo = "foo";
$bar = "bar";
function &GetRef(){
global $foo, $bar;
if(rand(0, 1) === 1){
return $foo;
}else{
return $bar;
}
}
$foo_or_bar =& GetRef();
$foo_or_bar = 'some other value';
var_dump($foo); // either one of this will be 'some other value'
var_dump($bar); // either one of this will be 'some other value'
Deryck Ethans also elaborated on this in PHP References: An In-Depth Look :
This [return by reference] is useful, for example, if you want to select a variable to modify using a function, for example by selecting an array element or node in a tree structure.
Sample code demonstrating selection of an array element via return-by-reference:
function &SelectArrayElement(&$array, $key){
return $array[$key];
}
$array = array(0, 1, 2);
$element =& SelectArrayElement($array, 0);
$element = 10;
var_dump($array); // array(10, 1, 2)
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Na. You cannot pass a reference to a function name. When passing a variable by reference, if you change its value in your function, that value will also be changed outside the function.
For example:
function test(&$var) {
$var = strtolower($var);
}
function second_test($var) {
$var = strtolower($var);
}
$var = 'PHP';
second_test($var);
echo $var;
echo "\r\n";
test($var);
echo $var;
This will display:
PHP
php
Since the second_test method does not have a variable passed by reference, the updated value is updated only inside the function. But the test method is passed by reference as a variable. This way the value will be updated inside and outside this function.
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I believe referring to byref arguments is not functions. For example:
function doStuff(&$value1, &$value2) {
...
}
is an acceptable use of byref because the doStuff () function must return 2 values. If it's just doStuff () only needed to affect one value, it would be more elegant if the function returned it, by value, of course.
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The bold part means this is useful if you want to store a reference to a variable instead of the value of that variable.
The link return example , on php.net, explains it pretty well, IMO.
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