程序24和程序25

$num = rand(1,99999);
strlen($num);
$arr_num = str_split($num);
array_reverse($arr_num);

strlen() 返回给定的字符串的长度。(Returns the length of the given string.)
str_split() 将字符串转换到一个数组中。(Converts a string to an array.)
array_reverse() 返回一个单元顺序相反的数组。(Returns a cell in the reverse order array.)

$five = rand(10000, 99999);
$arr_five = str_split($five);
if($arr_five[0]==$arr_five[4] && $arr_five[1]==$arr_five[3]){
    echo '回文数';
}