Check if a file exists using file_exists() function in PHP

In the PHP development process, it is usually necessary to read and write files to implement various functions. But before reading and writing files, we need to ensure that the file to be operated exists. Therefore, it becomes very important to check if the file exists. In PHP, we can use the file_exists() function to check whether a file exists.

The file_exists() function is a PHP function used to check whether a file or directory exists. This function takes a filename or file path as an argument and returns a Boolean value: true if the file or directory exists, false otherwise. The file_exists() function executes quickly and can check whether a local file or a remote URL file exists.

The following is a sample code that describes how to use the file_exists() function in PHP to check whether a file exists:

$filename = 'example.txt';
if (file_exists($filename)) {
    echo "文件存在";
} else {
    echo "文件不存在";
}

In the above code, we first define a variable $filename and set Its assigned value is 'example.txt'. Next, we use the file_exists() function to check whether the file exists. If the file exists, output "File exists", otherwise output "File does not exist".

In addition to checking local files, the file_exists() function can also be used to check whether remote URL files exist. If we need to check whether a remote URL file exists, we only need to pass the URL path to the file_exists() function. For example:

$url = 'https://www.example.com/example.txt';
if (file_exists($url)) {
    echo "文件存在";
} else {
    echo "文件不存在";
}

In the above code, we define a variable $url and assign it to the remote URL to be checked. We then use the file_exists() function to check if the URL file exists. If the file exists, output "File exists", otherwise output "File does not exist".

It should be noted that the path checked by the file_exists() function is not necessarily a file name. It can also be a directory name, which returns true if the directory exists, false otherwise. For example:

$dirname = 'example';
if (file_exists($dirname)) {
    echo "目录存在";
} else {
    echo "目录不存在";
}

In the above code, we define a variable $dirname and assign it to the directory to be checked. We then use the file_exists() function to check if the directory exists. If the directory exists, output "Directory exists", otherwise output "Directory does not exist".

In general, using the file_exists() function to check whether a file or directory exists is very simple and is often used in PHP programming. When operating files, reasonable use of the file_exists() function can improve the robustness and security of the code, thereby improving development efficiency.

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