PHP Manual: func_num

Description

int func_num_args ( void )

Returns the number of arguments passed into the current user-defined function. func_num_args() will generate a warning if called from outside of a user-defined function. This function cannot be used directly as a function parameter. Instead, its result may be assigned to a variable, which can then be passed to the function.

Note: Because this function depends on the current scope to determine parameter details, it cannot be used as a function parameter. If you must pass this value, assign the results to a variable, and pass the variable.

<?php
function foo() 
{
    $numargs = func_num_args();
    echo "Number of arguments: $numargs\n";
} 

foo(1, 2, 3);    // Prints 'Number of arguments: 3'
?>

func_num_args() may be used in conjunction with func_get_arg() and func_get_args() to allow user-defined functions to accept variable-length argument lists.