Function arguments
Information may be passed to functions via the argument list,
which is a comma-delimited list of variables and/or constants.
PHP supports passing arguments by value (the default),
passing by reference, and default argument values. Variable-length
argument lists are supported only in PHP 4 and later; see
Variable-length argument lists and the function references
for func_num_args(), func_get_arg(), and func_get_args()
for more information. A similar effect can be achieved in
PHP 3 by passing an array of arguments to a function:
Example 12-4. Passing arrays to functions
<?php
function takes_array($input)
{
echo "$input[0] + $input[1] = ", $input[0]+$input[1];
}
?>
Making arguments be passed by reference
By default, function arguments are passed by value (so that
if you change the value of the argument within the function,
it does not get changed outside of the function). If you
wish to allow a function to modify its arguments, you must
pass them by reference.
If you want an argument to a function to always be passed
by reference, you can prepend an ampersand (&) to the
argument name in the function definition:
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