To safely handle PHP file uploads, you need to verify the source and type, control the file name and path, set server restrictions, and process media files twice. 1. Verify the upload source to prevent CSRF through token and detect the real MIME type through finfo_file using whitelist control; 2. Rename the file to a random string and determine the extension to store it in a non-Web directory according to the detection type; 3. PHP configuration limits the upload size and temporary directory Nginx/Apache prohibits access to the upload directory; 4. The GD library resaves the pictures to clear potential malicious data.

InPHP,variablesarepassedbyvaluebydefault,meaningfunctionsorassignmentsreceiveacopyofthedata,whilepassingbyreferenceallowsmodificationstoaffecttheoriginalvariable.1.Whenpassingbyvalue,changestothecopydonotimpacttheoriginal,asshownwhenassigning$b=$aorp

The most direct way to find the last occurrence of a substring in PHP is to use the strrpos() function. 1. Use strrpos() function to directly obtain the index of the last occurrence of the substring in the main string. If it is not found, it returns false. The syntax is strrpos($haystack,$needle,$offset=0). 2. If you need to ignore case, you can use the strripos() function to implement case-insensitive search. 3. For multi-byte characters such as Chinese, the mb_strrpos() function in the mbstring extension should be used to ensure that the character position is returned instead of the byte position. 4. Note that strrpos() returns f

The reason why header('Location:...') in AJAX request is invalid is that the browser will not automatically perform page redirects. Because in the AJAX request, the 302 status code and Location header information returned by the server will be processed as response data, rather than triggering the jump behavior. Solutions are: 1. Return JSON data in PHP and include a jump URL; 2. Check the redirect field in the front-end AJAX callback and jump manually with window.location.href; 3. Ensure that the PHP output is only JSON to avoid parsing failure; 4. To deal with cross-domain problems, you need to set appropriate CORS headers; 5. To prevent cache interference, you can add a timestamp or set cache:f

AgeneratorinPHPisamemory-efficientwaytoiterateoverlargedatasetsbyyieldingvaluesoneatatimeinsteadofreturningthemallatonce.1.Generatorsusetheyieldkeywordtoproducevaluesondemand,reducingmemoryusage.2.Theyareusefulforhandlingbigloops,readinglargefiles,or

The COALESCE function is used to return the first non-null value in the parameter list and is suitable for processing NULL data. 1. The basic usage is to replace the NULL value, such as replacing the empty field with the default contact method; 2. It can be used to set the default value in aggregate query to ensure that 0 is returned instead of NULL when there is no data; 3. It can be used in conjunction with other functions such as NULLIF and IFNULL to enhance data cleaning and logical judgment capabilities.

The urlencode() function is used to encode strings into URL-safe formats, where non-alphanumeric characters (except -, _, and .) are replaced with a percent sign followed by a two-digit hexadecimal number. For example, spaces are converted to signs, exclamation marks are converted to!, and Chinese characters are converted to their UTF-8 encoding form. When using, only the parameter values ??should be encoded, not the entire URL, to avoid damaging the URL structure. For other parts of the URL, such as path segments, the rawurlencode() function should be used, which converts the space to . When processing array parameters, you can use http_build_query() to automatically encode, or manually call urlencode() on each value to ensure safe transfer of data. just

In PHP, the main difference between == and == is the strictness of type checking. The == operator performs type conversion when comparing, while === strictly checks the values ??and types without conversion. For example: "5"==5 returns true but "5"==5 returns false; 0==false is true but 0===false is false; null===0 is always false. You should use == when the type is independent or requires flexible comparison, such as user input processing; if the type must be consistent, such as the detection function returns false, validation null or boolean flag. It is recommended to use === first to avoid logic caused by type conversion