1查找字符位置函数:
strpos($str,$seach,[int]);查找search在$str中的第一次位置从int开始;
stripos($str,$seach,[int]);函数返回字符串在另一个字符串中第一次出现的位置。该函数对大小写不敏感
strrpos($str,search,[int]):查找search在$str中的最后一次出现的位置从int开始
strripos($str,search,[int]):同上,该函数对大小写不敏感
2.提取子字符串的函数
substr($str,int start,[int len])
strstr($str1,str2)
stristr() 功能同strstr,只是不区分大小写
strrchr() 从最后一次搜索到的字符处返回;用处:取路径中文件名
3.替换字符串的PHP字符串函数
str_replace(search,replace,source)查找search用replace替换在source中
str_ireplace(search,replace,$str):同上,该函数对大小写不敏感
strtr ($str ,$from ,$to )该函数返回 str 的一个副本,并将在 from 中指定的字符转换为 to 中相应的字符
$trans = array("hello" => "hi", "hi" => "hello");
echo strtr("hi all, I said hello", $trans);
?>
substr_replace($Str,$rep,$start[,length]):$str原始字符串,$rep替换后的新字符串,$start起始位置,$length替换的长度,该项可选
4、字符长度
int strlen($str)
5、比较字符函数
int strcmp($str1,$str2)$str1>= strcasecmp() 忽略大小写(同上)
strnatcmp("8","18")按自然排序比较字符串
strnatcasecmp()
6、分割成数组的PHP字符串函数
str_split($str,len)
split(search,$str,[int])
explode(search,$str,[int])把$str按search字符进行分割返回数组int是分割几次,后面的将不分割
7、去除空格:
ltrim() rtrim() trim()
8、加空格函数
chunk_split($str,2)向$str字符里面按2个字符就加入一个空格;
9、chr、ord--返回指定的字符或ascii
10、HTML代码有关函数
nl2br()使\n转换成
strip_tags($str,['
'])去除HTML和PHP标记
如:echo strip_tags($text, '
')
htmlspecialchars($str[,var])
11、字符大小写转换的PHP字符串函数
strolower(str)
stroupper(str)
ucfirst(str)将函数的第一个字符转换为大写
ucwords(str)将每个单词的首字母转换为大写
12、数据库相关的PHP字符串函数
addslashes(str)使str内单引号(')、双引号(")、反斜线(\)与 NUL字符串转换为\',\",\\。
magic_quotes_gpc = On :自动对 get,post,cookie的内容进行转义
get_magic_quotes_gpc():检测是否打开magic_quotes_gpc
stripslashes(): 去除字符串中的反斜杠

Reasons for PHPSession failure include configuration errors, cookie issues, and session expiration. 1. Configuration error: Check and set the correct session.save_path. 2.Cookie problem: Make sure the cookie is set correctly. 3.Session expires: Adjust session.gc_maxlifetime value to extend session time.

Methods to debug session problems in PHP include: 1. Check whether the session is started correctly; 2. Verify the delivery of the session ID; 3. Check the storage and reading of session data; 4. Check the server configuration. By outputting session ID and data, viewing session file content, etc., you can effectively diagnose and solve session-related problems.

Multiple calls to session_start() will result in warning messages and possible data overwrites. 1) PHP will issue a warning, prompting that the session has been started. 2) It may cause unexpected overwriting of session data. 3) Use session_status() to check the session status to avoid repeated calls.

Configuring the session lifecycle in PHP can be achieved by setting session.gc_maxlifetime and session.cookie_lifetime. 1) session.gc_maxlifetime controls the survival time of server-side session data, 2) session.cookie_lifetime controls the life cycle of client cookies. When set to 0, the cookie expires when the browser is closed.

The main advantages of using database storage sessions include persistence, scalability, and security. 1. Persistence: Even if the server restarts, the session data can remain unchanged. 2. Scalability: Applicable to distributed systems, ensuring that session data is synchronized between multiple servers. 3. Security: The database provides encrypted storage to protect sensitive information.

Implementing custom session processing in PHP can be done by implementing the SessionHandlerInterface interface. The specific steps include: 1) Creating a class that implements SessionHandlerInterface, such as CustomSessionHandler; 2) Rewriting methods in the interface (such as open, close, read, write, destroy, gc) to define the life cycle and storage method of session data; 3) Register a custom session processor in a PHP script and start the session. This allows data to be stored in media such as MySQL and Redis to improve performance, security and scalability.

SessionID is a mechanism used in web applications to track user session status. 1. It is a randomly generated string used to maintain user's identity information during multiple interactions between the user and the server. 2. The server generates and sends it to the client through cookies or URL parameters to help identify and associate these requests in multiple requests of the user. 3. Generation usually uses random algorithms to ensure uniqueness and unpredictability. 4. In actual development, in-memory databases such as Redis can be used to store session data to improve performance and security.

Managing sessions in stateless environments such as APIs can be achieved by using JWT or cookies. 1. JWT is suitable for statelessness and scalability, but it is large in size when it comes to big data. 2.Cookies are more traditional and easy to implement, but they need to be configured with caution to ensure security.


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