PHP中功能强大却很少使用的函数实例小结

<?php
function a(){}
$b = get_defined_functions();
print_r($b);
//也许会显示1000多个已定义了的函数）
?>

<?php
if (function_exists('a')) {
  echo "yes";
} else {
  echo "no";
}
function a(){}
// 显示 yes
?>

<?php
function a($b,$c)
{
  echo $b;
  echo $c;
}
call_user_func('a', "111","222");
call_user_func('a', "333","444");
//显示 111 222 333 444
?>

<?php
class a {
  function b($c)
  {
    echo $c;
  }
}
call_user_func(array("a", "b"),"111");
//显示 111
?>

<?php
function a($b, $c)
{
  echo $b;
  echo $c;
}
call_user_func_array('a', array("111", "222"));
//显示 111 222
?>

<?php
function a(&$b)
{
  $b++;
}
$c = 0;
call_user_func('a', &$c);
echo $c;//显示 1
call_user_func_array('a', array(&$c));
echo $c;//显示 2
?>

<?php
function a()
{
  echo func_num_args();
}
a(111, 222, 333);
//显示 3
?>

<?php
function a()
{
   echo func_get_arg(1);
}
a (111, 222, 333);
//显示 222
?>

<?php
function a()
{
  $numargs = func_num_args();
  $b = func_get_args();
  for ($i = 0; $i < $numargs; $i++) {
    echo $b[$i];
  }
}
a(111, 222, 333);
//显示 111 222 333
?>

<?php
$newfunc = create_function('$a,$b', 'return $a + $b;');
echo $newfunc;
echo $newfunc(2, 3);
//显示 lambda_1 5
?>

<?php
function a() {
  echo 222 ;
}
echo 111;
register_shutdown_function('a');
//显示 111 222
?>

<?php
class a
{
  function b ($c)
  {
   echo $c;
  }
}
register_shutdown_function (array ('a', 'b'), '111');
//显示 111
?>

declare (directive){
statement
}

<?
function foo($str) {
static $i = 0;
print "$str: $i<br>";
$i++;
}
register_tick_function("foo", "count");
declare (ticks = 6) {
for($i=0; $i<20; $i++) {
echo "$i<br>";
}
}
?>