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  • PHP get the first N characters of a string
    PHP get the first N characters of a string
    You can use substr() or mb_substr() to get the first N characters in PHP. The specific steps are as follows: 1. Use substr($string,0,N) to intercept the first N characters, which is suitable for ASCII characters and is simple and efficient; 2. When processing multi-byte characters (such as Chinese), mb_substr($string,0,N,'UTF-8'), and ensure that mbstring extension is enabled; 3. If the string contains HTML or whitespace characters, you should first use strip_tags() to remove the tags and trim() to clean the spaces, and then intercept them to ensure the results are clean.
    PHP Tutorial . Backend Development 262 2025-07-11 03:17:00
  • How to prevent session hijacking in PHP?
    How to prevent session hijacking in PHP?
    To prevent session hijacking in PHP, the following measures need to be taken: 1. Use HTTPS to encrypt the transmission and set session.cookie_secure=1 in php.ini; 2. Set the security cookie attributes, including httponly, secure and samesite; 3. Call session_regenerate_id(true) when the user logs in or permissions change to change to change the SessionID; 4. Limit the Session life cycle, reasonably configure gc_maxlifetime and record the user's activity time; 5. Prohibit exposing the SessionID to the URL, and set session.use_only
    PHP Tutorial . Backend Development 199 2025-07-11 03:15:51
  • PHP explode string by delimiter
    PHP explode string by delimiter
    In PHP, use the exploit() function to split strings by separator. The basic usage is exploit(separator, string, limit), where separator is the required separator, string is the string to be split, and limit is the optional parameter to limit the number of array elements. For example, $arr=explode(",","apple,banana,orange") will return ['apple','banana','orange']; continuous separators such as "a,,b" will produce empty string elements; if the separator is an empty word
    PHP Tutorial . Backend Development 653 2025-07-11 03:15:21
  • How Do Generators Work in PHP?
    How Do Generators Work in PHP?
    AgeneratorinPHPisamemory-efficientwaytoiterateoverlargedatasetsbyyieldingvaluesoneatatimeinsteadofreturningthemallatonce.1.Generatorsusetheyieldkeywordtoproducevaluesondemand,reducingmemoryusage.2.Theyareusefulforhandlingbigloops,readinglargefiles,or
    PHP Tutorial . Backend Development 569 2025-07-11 03:12:10
  • How do you handle exceptions in php using `try...catch` blocks?
    How do you handle exceptions in php using `try...catch` blocks?
    Using try...catch blocks in PHP is an effective way to manage errors and unexpected behavior. 1. An exception is an object thrown during execution, indicating that a problem occurs, such as calling a non-objective method or opening a non-existent file. 2. The try block contains code that may have errors, the catch block catches and handles exceptions, and obtains messages, codes and other information through $e. 3. Multiple catch blocks can be used to handle different types of exceptions in a specific to common order. 4. Exceptions can be thrown manually to verify input or execute business rules, but abuse should be avoided. 5. It is recommended to use meaningful exception messages, create custom exception classes appropriately, and note that finally blocks can be used for cleaning operations.
    PHP Tutorial . Backend Development 392 2025-07-11 03:09:41
  • What is PHP Dependency Injection and its benefits?
    What is PHP Dependency Injection and its benefits?
    DependencyinjectioninPHPisadesignpatternthatenhancesflexibilityandtestabilitybyallowingdependenciestobepassedintoclassesratherthanhardcoded.Insteadofcreatingdependenciesinsideaclass,suchas$this->db=newDatabase();,dependencyinjectionpassesthemviaco
    PHP Tutorial . Backend Development 675 2025-07-11 03:02:41
  • How to use substr_replace in PHP
    How to use substr_replace in PHP
    substr_replace is a function in PHP to replace the contents of the specified position in a string. Its syntax is substr_replace($string,$replace,$start,$length), where $start represents the start position and $length is an optional parameter that represents the replacement length. For example, substr_replace("Helloworld!","PHP", 6, 5) output HelloPHP! Common uses include: 1. Replace the content of the specified location, such as replacing "sunny" with "rainy&quo
    PHP Tutorial . Backend Development 866 2025-07-11 03:00:40
  • What is the role of the `__construct` and `__destruct` methods in php classes?
    What is the role of the `__construct` and `__destruct` methods in php classes?
    InPHP,__constructand__destructarespecialmethodsusedforobjectinitializationandcleanup.1.__constructrunsautomaticallywhenanobjectiscreated,allowingsetupactionslikeassigninginitialvaluesorconnectingtoadatabase.2.Itcanacceptargumentsandiscommonlyusedtoin
    PHP Tutorial . Backend Development 867 2025-07-11 03:00:02
  • php date to timestamp
    php date to timestamp
    There are two main ways to convert date strings to Unix timestamps in PHP. 1. Use the strtotime() function to be suitable for date strings in standard formats, such as "2024-12-2514:30:00", but the processing of non-standard or Chinese format is weak; 2. Use the DateTime::createFromFormat() method to accurately match the specified format, which is suitable for processing non-standard format data, such as user input or CSV data; 3. For date strings containing Chinese characters, they can be converted into standard format first through str_replace() or regular expression before parsing. When selecting a method, you need to judge based on the specific scene: use strto for simple scenes
    PHP Tutorial . Backend Development 998 2025-07-11 02:55:40
  • Does closing the browser destroy the PHP session?
    Does closing the browser destroy the PHP session?
    Close the browser will not automatically destroy the PHP session, depending on the session configuration. 1. By default, PHP uses session cookies without expiration time. Close the browser will delete the cookie, but the server-side session data still exists until it is cleaned up by the garbage collection mechanism; 2. If the expiration time of the cookie is manually set, closing the browser will not delete the cookie, and the user can still resume the session the next time he accesses; 3. To ensure that closing the browser ends the session, the default behavior or explicitly clear the cookie and session data; 4. Server-side cleanup is not instant, and it depends on configuration parameters such as session.gc_maxlifetime and garbage collection mechanism. Therefore, configure the session settings reasonably and implement
    PHP Tutorial . Backend Development 158 2025-07-11 02:54:01
  • How to change the session timeout in PHP?
    How to change the session timeout in PHP?
    Adjusting the session timeout in PHP requires modifying the configuration and code logic. 1. Modify the session.gc_maxlifetime parameter in php.ini, if set to 86400 seconds to extend the timeout. 2. Set session.cookie_lifetime to control the survival time of the browser cookie, such as set to 86400 seconds to maintain login status. 3. Use ini_set and session_set_cookie_params to dynamically set the timeout time, which is suitable for environments where php.ini cannot be modified. 4. Pay attention to problems that are easily overlooked in actual development such as garbage collection mechanism, file permissions, domain name sharing, etc., and ensure that
    PHP Tutorial . Backend Development 879 2025-07-11 02:44:51
  • PHP PDO fetch all prepared statement
    PHP PDO fetch all prepared statement
    Use the fetchAll() method of PDO to get all query results at once. Pay attention to parameter binding, error handling and return format selection. 1. Ensure that the SQL statement is correct and call execute() to perform preprocessing; 2. It is recommended to use PDO::FETCH_ASSOC mode to return the associative array of field name keys; 3. Turn on the exception mode to facilitate debugging problems; 4. Avoid the default PDO::FETCH_BOTH mode to save memory; 5. If necessary, use try-catch to catch the exception to confirm the cause of errors.
    PHP Tutorial . Backend Development 604 2025-07-11 02:43:51
  • How to pass a variable by value to a PHP function?
    How to pass a variable by value to a PHP function?
    In PHP, by default, the function passes variables by value, which means that the function receives a copy of the original variable value. 1. When you pass a variable to a function, the modification of the variable inside the function will not affect the original variable outside the function; 2. If you want to modify the original variable inside the function, you can achieve it by returning a new value and reassigning the value to the original variable after being called; 3. Although using global variables is feasible, it is usually not recommended because it will make the code difficult to maintain and debug; 4. PHP has internally optimized large data structures such as arrays or objects (such as copying on write), so the performance impact of value passing is usually very small. Therefore, when using value transfer, you need to pay attention to the above characteristics to ensure code accuracy and efficiency.
    PHP Tutorial . Backend Development 279 2025-07-11 02:34:11
  • How to count the number of active sessions in PHP?
    How to count the number of active sessions in PHP?
    In PHP, counting the number of active sessions can be achieved in three ways: one is to read the session file, scan the file starting with sess\_ in the specified directory, and judge whether it is counted as active based on the last modification time (such as within the last 30 minutes). The sample code can count the number of files that meet the conditions; the second is to use the database or cache to store the session status, update the last active time at the beginning of each session, and query the number of active sessions within the specified time; the third is to maintain the "online user" table, update the last active time during access, and implement statistics through timed cleaning and query. Different solutions are suitable for different scenarios, and file methods are available for simple purposes. It is recommended to use databases or cache mechanisms in large systems.
    PHP Tutorial . Backend Development 337 2025-07-11 02:27:31

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