PHP项目开发中最常用的自定义函数，php开发中，经常需要用到的。其实很多成熟的cms系统中都有的。

<?php
//alert提示
function alert($msg){
echo "<script>alert('$msg');</script>";
}
//把一些预定义的字符转换为 HTML 实体
function d_htmlspecialchars($string) {
if(is_array($string)) {
foreach($string as $key => $val) {
$string[$key] = d_htmlspecialchars($val);
}
} else {
$string = str_replace('&', '&', $string);
$string = str_replace('"', '"', $string);
$string = str_replace(''', ''', $string);
$string = str_replace('<', '<', $string);
$string = str_replace('>', '>', $string);
$string = preg_replace('/&(#\d;)/', '&\1', $string);
}
return $string;
}
//在预定义字符前加上反斜杠，包括 单引号、双引号、反斜杠、NULL，以保护数据库安全
function d_addslashes($string, $force = 0) {
if(!$GLOBALS['magic_quotes_gpc'] || $force) {
if(is_array($string)) {
foreach($string as $key => $val) $string[$key] = d_addslashes($val, $force);
}
else $string = addslashes($string);
}
return $string;
}
//生成随机字符串，包含大写、小写字母、数字
function randstr($length) {
$hash = '';
$chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz';
$max = strlen($chars) - 1;
mt_srand((double)microtime() * 1000000);
for($i = 0; $i < $length; $i++) {
$hash .= $chars[mt_rand(0, $max)];
}
return $hash;
}
//转换时间戳为常用的日期格式
function trans_time($timestamp){
if($timestamp < 1) echo '无效的Unix时间戳';
else return date("Y-m-d H:i:s",$timestamp);
}
//获取IP
function get_ip() {
if ($_SERVER["HTTP_X_FORWARDED_FOR"])
$ip = $_SERVER["HTTP_X_FORWARDED_FOR"];
else if ($_SERVER["HTTP_CLIENT_IP"])
$ip = $_SERVER["HTTP_CLIENT_IP"];
else if ($_SERVER["REMOTE_ADDR"])
$ip = $_SERVER["REMOTE_ADDR"];
else if (getenv("HTTP_X_FORWARDED_FOR"))
$ip = getenv("HTTP_X_FORWARDED_FOR");
else if (getenv("HTTP_CLIENT_IP"))
$ip = getenv("HTTP_CLIENT_IP");
else if (getenv("REMOTE_ADDR"))
$ip = getenv("REMOTE_ADDR");
else
$ip = "Unknown";
return $ip;
}
//计算时间差：默认返回类型为“分钟”
//$old_time 只能是时间戳，$return_type 为 h 是小时，为 s 是秒
function timelag($old_time,$return_type='m'){
if($old_time < 1){
echo '无效的Unix时间戳';
}else{
switch($return_type){
case 'h':
$type = 3600; break;
case 'm':
$type = 60; break;
case 's':
$type = 1; break;
case '':
$type = 60; break;
}
$dif = round( (time()-$old_time)/$type ) ;
return $dif;
}
}
//获取当前页面的URL地址
function url_this(){
$url = "http://".$_SERVER ["HTTP_HOST"].$_SERVER["REQUEST_URI"];
$return_url = "<a href='$url'>$url</a>";
return $return_url;
}
//跳转函数
function url_redirect($url,$delay=''){
if($delay == ''){
echo "<script>window.location.href='$url'</script>";
}else{
echo "<meta http-equiv='refresh' content='$delay;URL=$url' />";
}
}
} //end func

?>