PHP Manual
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func_num_args

(PHP 4 , PHP 5)

func_num_args --  Returns the number of arguments passed to the function

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.

<?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.

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func_get_args上一级function_exists