


Summary of basic operations on PHP arrays (recommended), summary of basic operations_PHP tutorial
Summary of basic PHP array operations (recommended), summary of basic operations
The concept of array
Array is a very important concept in PHP. We can think of an array as a collection of similar data. In fact, an array is an ordered graph.
PHP also provides over 70 built-in functions to operate on arrays.
Create array
Create an array using the array() language construct:
<?php $arr_age1 = array(18, 20, 25); // 或者: $arr_age2 = array("wang"=>18, "li"=>20, "zhang"=>25); // 空数组: $arr_age3 =array(); ?>
You can also use the array controller [] to create an array:
<?php $arr_age1[] = 18; $arr_age1[] = 20; $arr_age1[] = 25; // 或者: $arr_age2["wang"] = 18; $arr_age2["li"] = 20; $arr_age2["zhang"] = 25; ?>
Array key name and value
Array entities contain two items: key name and value.
In the following example of creating an array:
$arr_age1 = array(18, 20, 25); We allocate 3 array units (also called elements) to $arr_age1, whose values are 18, 20 and 25 respectively. The system will automatically assign three numerical serial numbers to these three array units, which are 0, 1 and 2 respectively. That is, the complete structure of the $arr_age1 array is:
Array ( [0] => 18 [1] => 20 [2] => 25 ) The serial number automatically assigned by this system is called the key name. This array of key names is called the index. Array (indexed array).
Of course, you can also manually specify the key name:
$arr_age1 = array( 0 => 18, 1 => 20, 2 => 25 );
Note: Manually specifying key names does not need to start from 0, and you do not need to specify key names in numerical order. When a new unit is added to the array without specifying a key name, the system will automatically add 1 to the largest numeric key in the existing array as the key name of the new unit.
When strings rather than numeric indexes are used as keys, the array is called an associative array:
$arr_age2 = array("wang"=>18, "li"=>20, "zhang"=>25); But in PHP, there is no obvious boundary between these two arrays, and both can Mix it up. Note that associative arrays are case-sensitive for key names.
Output array cell value
The output array cell value can be accessed using the following method:
echo $arr_age1[0];
//Output: 18
echo $arr_age2["wang"];
//Output: 18 In some cases, for debugging, you may need to output the data and structure of the entire array. In this case, you need to use the print_r() or var_dump() function. For details, see PHP print_r and var_dump output array
Operation array unit
You can operate array units like ordinary variables, such as:
<?php $arr_age2 = array("wang"=>18, "li"=>20, "zhang"=>25); $arr_age2["wang"] = $arr_age2["wang"] + 10; ?>
Now $arr_age2 is:
Array ( [wang] => 28 [li] => 20 [zhang] => 25 )
To check if an array cell is set, use isset() .
Destroy array
Use the unset() function to destroy an array cell or an entire array:
<?php unset($arr_age1[0]); unset($arr_age1); ?>
Multidimensional array
If the values in the array are also arrays, we call such an array a recursive array or a multidimensional array.
Example:
<?php $all = array( "fruits" => array( "a"=>"orange", "b"=>"banana", "c"=>"apple"), "ages" => array( 18, 20, 25 ) ); echo $all["fruits"]["c"]; //输出apple echo $all["ages"][0]; //输出18 ?>
The above summary of basic PHP array operations (recommended) is all the content shared by the editor. I hope it can give you a reference, and I hope you will support Bangkejia.

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.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

Atom editor mac version download
The most popular open source editor

WebStorm Mac version
Useful JavaScript development tools

SecLists
SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function
