4.15.6 Variable parameter counts: func_num_args(), func_get_arg(), and func_get_args()This is NOT the latest copy of this book; click here for the latest version.
int func_num_args ( )
mixed func_get_arg ( int arg_num)
array func_get_args ( )
The printf() function we examined previously is able to take an arbitrary number of parameters. That is, it could take just one parameter, or five, or fifty, or five hundred - it can take as many as are passed into it by the user. This is known as a variable-length parameter list, and it is automatically implemented in your user functions. For example:
<?php
function some_func($a, $b) {
$j = 1;
}
some_func(1,2,3,4,5,6,7,8);
?>
Here the function some_func() is defined to only take two parameters, $a and $b, but we call it with eight parameters and the script should run without a problem. In that example, 1 will be placed into $a, and 2 will be placed into $b, but what happens to the other parameters?
Coming to your rescue are three functions: func_num_args(), func_get_arg(), and func_get_args(), of which the first and last take no parameters. To get the number of arguments that were passed into your function, call func_num_args() and read its return value. To get the value of an individual parameter, use func_get_arg() and pass in the parameter number you want to retrieve to have its value returned back to you. Finally, func_get_args() returns an array of the parameters that were passed in. Here's an example:
<?php
function some_func($a, $b) {
for ($i = 0; $i < func_num_args(); ++$i) {
$param = func_get_arg($i);
echo "Received parameter $param.\n";
}
}
function some_other_func($a, $b) {
$param = func_get_args();
$param = join(", ", $param);
echo "Received parameters: $param.\n";
}
some_func(1,2,3,4,5,6,7,8);
some_other_func(1,2,3,4,5,6,7,8);
?>
Using func_num_args() alone you can easily implement function error checking. You can, for example, start off each of your functions by checking to make sure func_num_args() is what you are expecting, and, if not, exit. Once you add func_get_arg() into the mix, however, you should easily be able to create your own functions that work with any number of parameters.
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