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  • How long does it take to learn HTML?
    How long does it take to learn HTML?
    Yes,learningHTMLcantakejustafewweeksforbasics.Inthefirstweek,you’llgrasptags,elements,structure,andcreatesimplecontentlikeheadings,links,andimages.Overthenextfewweeks,you’llbuildrealpagesusingforms,semantictags,andlayoutelements.Advancedtopicslikeacc
    HTML Tutorial . Web Front-end 821 2025-07-14 02:40:22
  • PHP undefined index $_GET
    PHP undefined index $_GET
    The PHPUndefinedIndex:$_GET error is because the unpassed GET parameter key is accessed. The error occurs when trying to read a parameter that does not exist in the URL, for example using echo$_GET['id'] but the URL does not have?id=123. Avoiding methods include: 1. Use isset($_GET['id']) to determine whether the key exists; 2. Use the ternary operator to set the default value such as $id=isset($_GET['id'])? $_GET['id']:null; 3. Choose whether to use empty() or array_key_exists() according to your needs. Development suggestions include: not directly use unverified parameters and unification
    PHP Tutorial . Backend Development 780 2025-07-14 02:39:51
  • mysql change column data type
    mysql change column data type
    Modify MySQL field type with ALTERTABLE...MODIFY or CHANGE statement 1.MODIFY is used to change the type only, such as ALTERTABLEusersMODIFYageVARCHAR(10); 2. CHANGE can be changed at the same time, such as ALTERTABLEusersCHANGEageuser_ageVARCHAR(10); pay attention to data conversion risks, such as INT to VARCHAR lossless, otherwise an error may occur; the original constraints such as NOTNULL, DEFAULT, etc. must be added during operation; modifying the type may lock table reconstruction, affecting performance, and it is recommended to execute at low peaks; common scenarios include VA
    Mysql Tutorial . Database 403 2025-07-14 02:39:31
  • PHP undefined index after json_decode
    PHP undefined index after json_decode
    The problem with PHPundefinedindexafterjson_decode occurs mainly because of accessing non-existent keys. 1. Ensure that json_decode is executed correctly, check the JSON string format and use json_last_error() to determine whether the parsing is successful; 2. Use isset() or array_key_exists() to check whether it exists before accessing the key. The nested structure needs to be judged layer by layer; 3. Debug the output data structure through var_dump() or print_r() to confirm that the key name, hierarchy and type are correct; 4. Use the null merge operator?? to set the default value to avoid undefined index errors, improve code security and
    PHP Tutorial . Backend Development 233 2025-07-14 02:38:51
  • PHP convert ASCII value to character using chr
    PHP convert ASCII value to character using chr
    In PHP, using the chr() function can convert the ASCII value to the corresponding character. 1.chr() receives an integer parameter (ASCII code) and returns the corresponding characters; 2. The valid range is 0 to 127, and the results outside this range may vary from system to system; 3. Common uses include generating line breaks (chr(10)), carriage return (chr(13)), tab characters (chr(9)) and spaces (chr(32)); 4. Notes: Floating point numbers will be truncated, multi-byte characters need to be processed by mb_ function, and some ASCII codes have no visual output.
    PHP Tutorial . Backend Development 630 2025-07-14 02:38:10
  • php iterate over a date range
    php iterate over a date range
    It is recommended to use the DatePeriod class to traverse date ranges in PHP. 1. The DatePeriod class was introduced from PHP5.3, and date traversal is implemented by setting the start date, end date and interval. For example, generate a date list from 2024-01-01 to 2024-01-05, which does not include the end date by default; 2. If you need to include the end date, you can adjust the end date or set the INCLUDE_END_DATE parameter; 3. The manual loop method can also complete the traversal using the DateTime object and the modify() method, which is suitable for scenarios where step size needs to be flexibly controlled; 4. Pay attention to the time zone problem that should be explicitly set to avoid the system's default time zone affecting the result; 5. PHP automatically handles leap years
    PHP Tutorial . Backend Development 149 2025-07-14 02:37:50
  • Applying visual effects using css filter property
    Applying visual effects using css filter property
    The filter attribute of CSS can add a variety of visual effects to web elements. Common filters include 1.grayscale() grayscale processing, 2.sepia() browning, 3.saturate() saturation adjustment, 4.hue-rotate() hue transformation, 5.invert() color inversion, 6.brightness() brightness adjustment, 7.contrast() contrast adjustment, 8.blur() blur, 9.drop-shadow() shadow; multiple filters can be superimposed and smooth animations can be achieved with transition. They are suitable for hover interaction, background effects and other scenarios, but performance and compatibility issues need to be paid attention to.
    CSS Tutorial . Web Front-end 423 2025-07-14 02:37:31
  • Key Differences and Use Cases for HTML class and id Attributes
    Key Differences and Use Cases for HTML class and id Attributes
    Id is used to uniquely identify elements, such as navigation bar, footer; class is used to reusable styles, such as buttons, and status switching. 1. The id must be unique, suitable for anchor positioning and JavaScript precise operation; 2. Class can be used for multiple elements, supports multiple selection and combination, and is suitable for component design; 3. The priority of id in CSS is higher than class; 4. Use id for layout, and class for interactive logic; 5. The naming should be clear and semantic to avoid abuse or vague description.
    HTML Tutorial . Web Front-end 294 2025-07-14 02:37:11
  • What is the HTML DOM (Document Object Model)?
    What is the HTML DOM (Document Object Model)?
    TheHTMLDOMisaprogramminginterfacethatrepresentsanHTMLdocumentasatree-likestructure,enablingJavaScripttointeractwithandmanipulatewebpages.WhenabrowserloadsHTML,itparsesthecodeintoaDOMtreewhereeachelementbecomesanode,andnestedelementsformparent-childre
    HTML Tutorial . Web Front-end 486 2025-07-14 02:36:52
  • PHP prepared statement example
    PHP prepared statement example
    Preprocessing statements can effectively prevent SQL injection and improve execution efficiency in PHP database operations. When inserting data using MySQLi, use prepare() to define the statement, bind_param() to bind parameters. After multiple executions, you only need to modify and change the variable and call execute(); when querying, use prepare() and bind_param() to pass parameters, and then bind the result variables through bind_result() and obtain data with fetch(); if PDO is used, similar functions can be achieved through named parameters and array parameters, such as prepare() and pass parameters with execute(), and pass parameters through fetch(PDO::FETCH_ASSOC
    PHP Tutorial . Backend Development 844 2025-07-14 02:36:21
  • What are the best text editors or IDEs for writing HTML?
    What are the best text editors or IDEs for writing HTML?
    Choosing the right HTML editing tool can significantly improve development efficiency. There are four mainstream tools: 1. VisualStudioCode is suitable for lightweight and fast development, open source, and has a strong plug-in ecosystem, supporting intelligent completion, real-time preview and Emmet rapid generation structure; 2. SublimeText provides a one-stop development experience, fast response speed, simple interface, supports multi-cursor editing and rich shortcut key operations; 3. Brackets is more suitable for beginners or design-oriented users, providing real-time preview and inline editing functions, which are easy to learn and visual adjustment; 4. WebStorm is aimed at professional development, deeply integrating multiple technology stacks, with powerful error detection and repair capabilities, and supports debugging and version control. According to project
    HTML Tutorial . Web Front-end 259 2025-07-14 02:36:01
  • how to connect to mysql from node.js
    how to connect to mysql from node.js
    To connect MySQL data to Node.js application, 1. Install the mysql2 module; 2. Create a connection configuration, including host, user, password, database and other information; 3. Establish a connection and handle errors; 4. Execute SQL queries and process results; 5. Close the connection or use the connection pool to manage the connection; Common problems include network blockage, insufficient account permissions, firewall restrictions, password errors and SSL connection problems. Follow the steps to troubleshoot.
    Mysql Tutorial . Database 117 2025-07-14 02:35:21
  • What is Dependency Injection and why is it important in php development?
    What is Dependency Injection and why is it important in php development?
    DependencyInjection(DI)solvestightcouplinginPHPcodebyallowingexternalinjectionofdependencies,improvingflexibilityandtestability.Insteadofclassescreatingorlocatingtheirowndependencies,theyreceivethemfromoutside,makingiteasiertoswapimplementations,usem
    PHP Tutorial . Backend Development 561 2025-07-14 02:34:20
  • What is the difference between a function expression and a function declaration in PHP?
    What is the difference between a function expression and a function declaration in PHP?
    The main difference between function expressions and function declarations in PHP is to improve behavior and usage scenarios. Function declarations start with the function keyword, will be promoted and can be called before definition; suitable for scenarios where scripts are available anywhere, no conditional definition is required, and top-down readability is required. Function expressions assign functions to variables and will not be promoted. They must be defined first and then called; they are suitable for scenarios where conditions require the creation, use of closures or anonymous functions and are passed as parameters. The two are the same in terms of functional characteristics, but the creation and access timing are different.
    PHP Tutorial . Backend Development 471 2025-07-14 02:34:01

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