PHP项目中最常用的函数

<?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;)/', '&', $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 

?>