In PHP you can do this:
function something() {
foreach (func_get_args() as $arg)
echo $arg;
}
something(1, 3); //echoes "13"
This works fine for arguments passed by value, but what if I want them to be passed by reference? like this:
function something_else() {
foreach (func_get_args() as $arg)
$arg *= 2;
}
$a = 1;
$b = 3;
something_else($a, $b);
echo $a . $b; //should echo "26", but returns "13" when I try it
Is this possible in PHP?
The question seems horrible, but lets humour you. Below is a horrible hack, but you could send across a single argument which contains the items that you want to work with.
function something_else($args) {
foreach ($args as &$arg) {
$arg *= 2;
}
}
$a = 1;
$b = 3;
something_else(array(&$a, &$b));
echo $a . $b; // 26
No. You cannot. The declaration of a prameter passed by ref is explicit as function something(&$arg1, &$arg2). If you don't know the number of parameters at compile time, you can do something like this:
function something_else($args) {
foreach ($args as $arg)
$GLOBALS[$arg] *= 2;
}
$a = 1;
$b = 3;
something_else(array('a', 'b'));
echo $a . $b; //returns "26"
Basically the code passes to the function the names of the params the function will modify. $GLOBALS holds references to all defined variables in the global scope of the script. This means if the call is from another function it will not work:
function something_else($args) {
foreach ($args as $arg)
$GLOBALS[$arg] *= 2;
}
function other_function(){
$a = 1;
$b = 3;
something_else(array('a', 'b'));
echo $a . $b; //returns "13"
}
other_function();
triggers notices undefined indexes a and b. So another approach is to create an array with references to the variables the function will modify as:
function something_else($args) {
foreach ($args as &$arg)
$arg *= 2;
}
function other_fucntion(){
$a = 1;
$b = 3;
something_else(array(&$a, &$b));
echo $a . $b; //returns "26"
}
other_fucntion();
Note the & on the foreach line. It is needed so not to create a new variable iterating over the array. PHP > 5 needed for this feature.
$GLOBALSYou can do it this way but it uses call-time pass by reference which is deprecated in PHP 5.3:
function something_else() {
$backtrace = debug_backtrace();
foreach($backtrace[0]['args'] as &$arg)
$arg *= 2;
}
$a = 1;
$b = 3;
something_else(&$a, &$b);
echo $a . $b;
