


Some very strange problems often occur in sessions in PHP. Many of these problems are small details. It may be difficult for PHP beginners to find out what the reasons are. Today we have listed almost all the problems caused or caused by sessions. The problems are collected together and the solutions are given one by one. Students in need can take a look. If there are better friends, they can provide them to me.
1>Error message
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Warning: Cannot send session cookie - headers already sent
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The cause of the problem is that when session_start() is used in the program, actual html content has been output before. Even if a message is echoed or printed, the output generated by the echo or print statement is the actual html content output. The solution to this type of problem is to move session_start() to the first line of the program. 2>Error message
代码如下 | 复制代码 |
Warning: open(F:/webphpsessiondatasess_76666aecf239891edc98b5, O_RDWR) failed |
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Warning: open(F:/webphpsessiondatasess_76666aecf239891edc98b5, O_RDWR ) failed
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session.save_path和session.cookie_path 设置置为 session_save_path = c:temp session.cookie_path = c:temp |
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session.save_path and session.cookie_path settings are set to
session_save_path = c:temp |
代码如下 | 复制代码 |
错误提示 Warning: Trying to destroy uninitialized session in |
3>
代码如下 | 复制代码 |
echo SID; |
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echo SID; |
5> There is no output before calling the header function. Although I include a config.php file, there is no output in the config.php file. Why does the session still report the same error as question 1? Well, is it because I used session_start() before the header?
I carefully checked your PHP program and found that there is indeed no output before referencing header(), and there is no output in your include file!
But do you use the cursor keys to move the check after the end statement of the PHP code?>? Then you will find that after ?>, there is a blank line or a few spaces. If you delete these blank lines or spaces, the problem will be solved.
Note: This problem will appear in PHP4.1.2.
6> After using session to log in to the main page, how can I use session to restrict login on other pages? . .
Solution:
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session_start();
echo "You are not logged in";
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7> Use session_register() to register the session variable. However, when using header or JavaScript redirection statement, the variable value registered by the session cannot be accessed in the following page.
Program snippet in question:
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session_start(); $ok = ‘love you’;
header("location : next.php");
session_start(); |
Solution: When you use functions such as header function or window.location, the session variables registered on your previous page will be easily lost.
代码如下 | 复制代码 |
session_start(); $username = ‘;stangly.wrong’;; session_register(’;username’;); echo $HTTP_SESSION_VARS['username']; echo ‘; ’;; echo _SESSION['username']; ?> 10> |
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header("Location: next.php" . "?" .SID); |
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session_register('data';); data=array(1,2,3,4); |
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session_start();
$username = ‘;stangly.wrong’;;
session_register(’;username’;);
echo $HTTP_SESSION_VARS['username'];
echo ‘; ’;; echo _SESSION['username']; ?> 10> |
What is the difference between session_unregister() and session_destroy()?
The main function of the session_unregister() function is to unregister the current session variable. However, it should be noted that if you use HTTP_SESSION_VARS or _SESSION to reference the session variable in the current page, then you may need to cooperate with unset() to unset the session variable.
And session_destroy() clears the current session environment. This means that after you use the session_destroy() function, it is no longer possible to use session_is_registered() to detect session variables. But it should be noted that it cannot clear the session in the global or use the session cookie. So before using session_destroy, it is best not to use HTTP_SESSION_VARS _SESSION to access the session.
Routine:
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if(isset(_COOKIE[session_name()] )) { |
unset(_COOKIE[session_name()]);
www.bkjia.comtruehttp: //www.bkjia.com/PHPjc/632247.htmlTechArticleSome strange problems often occur in sessions in php. Many of these problems are small details. For php It may be difficult for beginners to discover the reason. Today we have put together almost everything...
php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。

在PHP中,可以利用implode()函数的第一个参数来设置没有分隔符,该函数的第一个参数用于规定数组元素之间放置的内容,默认是空字符串,也可将第一个参数设置为空,语法为“implode(数组)”或者“implode("",数组)”。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。


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