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  • PHP check if index exists in array
    PHP check if index exists in array
    In PHP, you should use isset() or array_key_exists(). 1. Use isset() to determine whether the key exists and the value is not null, which is suitable for most conventional scenarios; 2. Use array_key_exists() to only check whether the key exists, regardless of whether the value is null, which is suitable for stricter judgments; 3. For multi-dimensional arrays, it is necessary to judge layer by layer in combination with conditions, and can be used with isset() or array_key_exists(); in addition, attention should be paid to avoid directly accessing keys that are not confirmed to exist, and use is_array() to check when the variable type is not determined. Turning on error reporting in the development stage will help to find problems.
    PHP Tutorial . Backend Development 991 2025-07-12 02:50:21
  • What are the differences and use cases for html textarea and input type text?
    What are the differences and use cases for html textarea and input type text?
    The main difference is that textarea supports multiple lines of text input, while inputtext is only available in a single line. 1. Use inputtype="text" to be suitable for short and single-line user input, such as username, email address, etc., and can set maxlength to limit the number of characters. The browser provides automatic filling function, making it easier to uniformly style across browsers; 2. Use textarea for scenarios that require multiple lines of input, such as comment boxes, feedback forms, support line breaks and paragraphs, and can control the size through CSS or disable the adjustment function. Both support form features such as placeholders and required fills, but textarea defines the size through rows and cols, and input uses the size attribute.
    HTML Tutorial . Web Front-end 815 2025-07-12 02:48:42
  • Comparing CSS `display: none` and `visibility: hidden`
    Comparing CSS `display: none` and `visibility: hidden`
    The main difference between display:none and visibility:hidden is layout impact and accessibility. 1.display:none removes elements completely from the page and does not take up space, screen readers usually ignore it; 2.visibility:hidden hides elements but retains their space, and may still be read by screen readers in some cases. When choosing, consider whether the layout structure needs to be preserved or whether access to content is allowed: the former is suitable for scenarios that completely hide and exclude interactions, such as inactive tabs, and the latter is suitable for situations where the layout is stable and may be redisplayed quickly, such as animation transitions. In addition, visibility:hidden can be implemented through opacity
    CSS Tutorial . Web Front-end 944 2025-07-12 02:48:20
  • how to sort a multidimensional php array by a key
    how to sort a multidimensional php array by a key
    To sort multidimensional PHP arrays by specific keys, use the usort() function. 1. Use usort() with a custom comparison function to realize sorting through the spaceship operator or traditional comparison method; 2. If you want to sort in descending order, just change the comparison value; 3. It can be encapsulated into a reusable function to support different keys and sorting directions. For example, sort_by_key($people,'age') can be sorted in ascending order of age.
    PHP Tutorial . Backend Development 460 2025-07-12 02:48:01
  • how to access a php array element with a variable key
    how to access a php array element with a variable key
    In PHP, the use of variables as array keys is fully supported and is suitable for handling data with uncertain structures. First, use variables as array keys to dynamically obtain the value, for example: $key='name';$array=['name'=>'John']; echo$array[$key]; this allows you to flexibly deal with APIs or dynamic data. Secondly, before accessing, you should use isset() to determine whether the key exists to avoid errors. Third, logic can be encapsulated in loops or functions, such as traversing the field list to extract valid data or encapsulating the getValue function to improve reusability. Fourth, it is recommended to simplify the default value processing with the ?? operator, especially for nested arrays, ensuring the code is concise and safe. master
    PHP Tutorial . Backend Development 235 2025-07-12 02:47:41
  • How to create a 'back to top' button with HTML and JavaScript?
    How to create a 'back to top' button with HTML and JavaScript?
    To add the "Back to Top" button, first create the button element in HTML and set the id, such as ↑ back to top; then set the fixed positioning, lower right corner position and hide the default display through CSS, and add styles such as background color, rounded corners and shadows; then listen to scroll events in JavaScript, and display the button when the scroll distance exceeds the set value (such as 300 pixels), otherwise hide it; finally bind the click event for the button, and use window.scrollTo({top:0, behavior:'smooth'}) to achieve a smooth return to the top effect.
    HTML Tutorial . Web Front-end 222 2025-07-12 02:46:51
  • What are the del and ins tags used for?
    What are the del and ins tags used for?
    The and tags in HTML are used to mark deleted or inserted text in a document to display modifications or revisions. It indicates deletion, which is displayed in strikethrough style by default, and the datetime attribute can be added to record the deletion time; for example: outdatedcontent. It indicates insertion, which is displayed in an underscore style by default. It also supports the datetime attribute to record the insertion time; for example: newlyaddedtext. These two tags are commonly used for version control, content updates, collaboration tools and improved accessibility experience, and are suitable for meaningful changes rather than minor corrections.
    HTML Tutorial . Web Front-end 786 2025-07-12 02:45:52
  • Structuring Content with HTML Headings and Paragraphs
    Structuring Content with HTML Headings and Paragraphs
    When writing web content, you need to pay attention to the title and paragraph structure to improve the reading experience and SEO effect. 1. The title level should be clear. A page should only use one h1 as the main title, h2 as the title of the big section, and h3 subdivides the subsections to avoid multiple h1, skip grades or keyword piles up; 2. The paragraph should be controlled in three to four lines, and the key points should be directly mentioned at the beginning, and if necessary, use the ul list to enhance readability; 3. Appropriately use the subtitles of h2 and h3 to guide readers' attention, facilitate information search and optimize search engine recognition.
    HTML Tutorial . Web Front-end 557 2025-07-12 02:44:42
  • How to create a simple popup or modal with HTML, CSS, and JS?
    How to create a simple popup or modal with HTML, CSS, and JS?
    To achieve a basic pop-up effect, you need to follow the following steps: 1. Structure: Use HTML to create trigger buttons, mask layer and pop-up content area; 2. Style: Set default hidden, centered layout, mask background and close button styles through CSS; 3. Interaction: Use JavaScript to bind click events to control pop-up display and hide, and can expand the ESC key closing function; 4. Optimization: Add CSS animation to improve user experience. The entire process does not require a third-party library, which is suitable for quickly realizing basic pop-up functions.
    HTML Tutorial . Web Front-end 333 2025-07-12 02:42:22
  • How to create a range slider with the range input type?
    How to create a range slider with the range input type?
    To add a scope slider to a web page, use HTML elements. 1. The basic structure is to set the type to range, and define the range and initial value through min, max and value attributes; 2. The current slider value can be displayed in conjunction with JavaScript to improve user interaction experience; 3. Pay attention to browser compatibility issues when adjusting styles using CSS; 4. Applicable scenarios include age selection, volume control, price filtering, etc., but are not suitable for precise input or fine operation on the mobile terminal.
    HTML Tutorial . Web Front-end 208 2025-07-12 02:38:31
  • PHP remove specific characters from a string
    PHP remove specific characters from a string
    There are three ways to remove characters that do not need in PHP: 1. Use str_replace to delete specified characters, which is suitable for clearly knowing which characters to delete; 2. Use preg_replace to delete characters that comply with regular rules, which is suitable for processing a specific type of character such as non-alphanumeric characters; 3. Use trim, ltrim or rtrim to remove the beginning and end of string characters, which is suitable for cleaning user input and other scenarios.
    PHP Tutorial . Backend Development 742 2025-07-12 02:37:20
  • how to sort a php array by value
    how to sort a php array by value
    Tosortaphparraybyvalue, Usebuilt-Infunction Basedonkey Action Direction: 1.usesort () ForindexedarrAyswithnerickeysandascendingorder; 2.UsaSort () TopreservecustomKeyswhilesortingvaluesinasca order;
    PHP Tutorial . Backend Development 495 2025-07-12 02:36:41
  • How to use HTML for building email newsletters?
    How to use HTML for building email newsletters?
    The key to building email communications using HTML is compatibility and structural simplification. 1. Use table layout to replace Flexbox or Grid to ensure stable display in major mailbox clients; 2. All CSS styles need to be written inline to avoid relying on external style sheets; 3. Images should be clearly set width and add alternative text, and the buttons should be simulated with linked table cells; 4. It must be tested on multiple mailbox clients and devices, and use tools such as Litmus or EmailonAcid to ensure consistent results. Following the above points can improve the compatibility and actual effect of HTML emails.
    HTML Tutorial . Web Front-end 287 2025-07-12 02:35:41
  • Difference between margin and padding in css
    Difference between margin and padding in css
    InCSS,marginandpaddingcontrolspacingexternallyandinternally,respectively.1.Marginsetsspaceoutsideanelement,affectingspacingbetweenelementswithoutalteringitssize.2.Paddingsetsspaceinsideanelement,increasingitssizeandpushingcontentawayfromtheedges.3.Ma
    CSS Tutorial . Web Front-end 489 2025-07-12 02:30:31

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