PHP determines whether a file is writable

PHP determines whether a file or directory is writable

In PHP, the is_writable() function can be used to determine whether a file/directory is writable. , details are as follows:

Reference

is_writable — Determine whether the given file name is writable.

Description

bool is_writable (string $filename)

Returns TRUE if the file exists and is writable. (The $filename parameter can be a directory name, that is, check whether the directory is writable.)

Note:

PHP may only be able to run the webserver as the username (usually as 'nobody') to access files, does not count against safe mode restrictions.

is_writable() Example

<?php
$filename = &#39;test.txt&#39;;
if (is_writable($filename)) {
    echo &#39;The file is writable&#39;;
} else {
    echo &#39;The file is not writable&#39;;
}
?>

Note: is_writeable() is an alias of is_writable()!

In order to be compatible with various operating systems, you can customize a writable function. The code is as follows:

/**
 * 判断 文件/目录 是否可写（取代系统自带的 is_writeable 函数）
 *
 * @param string $file 文件/目录
 * @return boolean
 */
function new_is_writeable($file) {
    if (is_dir($file)){
        $dir = $file;
        if ($fp = @fopen("$dir/test.txt", 'w')) {
            @fclose($fp);
            @unlink("$dir/test.txt");
            $writeable = 1;
        } else {
            $writeable = 0;
        }
    } else {
        if ($fp = @fopen($file, 'a+')) {
            @fclose($fp);
            $writeable = 1;
        } else {
            $writeable = 0;
        }
    }
 
    return $writeable;
}

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