What should I do if php file_exists has no effect?

PHP's file_exists() function is used to check whether a file or directory exists. Returns TRUE if present, FALSE otherwise. You need to pay attention to the following issues when using it:

1. Path problem
   The file_exists() function is very sensitive to the processing of file paths. Spaces, special characters, slash directions, etc. in the path will affect the judgment results. . The correct path should be an absolute path, such as: /var/www/html/test.php.
2. File permissions issue
   In Linux, file permissions are represented by three numbers. The first number represents the owner's permissions, the second number represents the group permissions, and the third number represents other people's permissions. . Among them, 0 means no permission, 1 means execution permission, 2 means write permission, and 4 means read permission. The permissions of the file/folder do not meet the requirements, the program cannot read it, and the file_exists() function will also fail.
3. Other system issues
   In Windows systems, the file_exists() function is not subject to permission restrictions, but is sensitive to the case of file names. In Unix/Linux systems, file names are not case-sensitive, but the file_exists() function is case-sensitive by default. You can avoid this problem by using the strcasecmp() or strnatcasecmp() function instead of the default strcmp() function for string comparison.

The following is a sample code:

<?php
$file = &#39;/var/www/html/test.txt&#39;;// 文件路径
if (file_exists($file)) {
    echo "文件存在";
} else {
    echo "文件不存在";
}
?>

If the above code cannot correctly determine whether the file exists, then you need to carefully check the file path, file permissions, and system environment issues. At the same time, other alternative functions can also be used to complete the same function, such as is_file(), stat(), etc.

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