PHP is_writable()用法及代码示例

PHP中的is_writable()函数用于检查指定的文件是否可写。文件名作为参数发送到is_writable()函数，如果文件名存在且可写，则返回True。
目录的名称也可以是is_writable()函数的参数，该函数允许检查目录是否可写。

用法:

is_writable(file)

使用的参数：
PHP中的is_writable()函数接受一个参数。

• file :它是指定文件的必需参数。

返回值：
如果文件名存在且可写，则返回True。

异常：

1. 失败时发出E_WARNING。
2. 此函数的结果被缓存，因此使用clearstatcache()函数清除缓存。
3. is_writable()函数为不存在的文件返回false。

例子：

Input : $myfile = "gfg.txt";
        if(is_writable($myfile)) 
        {
           echo ("$myfile file is writable!");
        } 
        else 
        {
           echo ("$myfile file is not writable!");
        }
Output : gfg.txt file is writable!

Input : $permissions = fileperms("gfg.txt");
        $perm_value = sprintf("%o", $permissions);
        $myfile = "gfg.txt";
       
        if (is_writable($myfile)) 
        {
          echo ("$myfile file is writable and
          it has the following file permissions : $perm_value");
        } 
        else 
        {
          echo ("$myfile file is not writable and
          it has the following file permissions : $perm_value");
        }

Output : gfg.txt file is writable and it has the following file permissions : 0664

以下示例程序旨在说明is_writable()函数。

程序1

<?php  
$myfile = "gfg.txt"; 
  
// checking whether the file is writable or not 
if(is_writable($myfile))  
{ 
 echo ("$myfile file is writable!"); 
}  
else 
{ 
 echo ("$myfile file is not writable!"); 
} 
?>

输出：

 gfg.txt file is writable!

程序2

<?php  
// checking permissions of the file 
$permissions = fileperms("gfg.txt"); 
$perm_value = sprintf("%o", $permissions); 
  
// Clearing the File Status Cache  
clearstatcache(); 
  
$myfile = "gfg.txt"; 
  
// checking whether the file is writable or not 
if(is_writable($myfile))  
{ 
 echo ("$myfile file is writable and 
   it has the following file permissions : $perm_value"); 
}  
else 
{ 
 echo ("$myfile file is not writable and
   it has the following file permissions : $perm_value"); 
} 
  
// Clearing the File Status Cache  
clearstatcache(); 
?>

输出：

gfg.txt file is writable and it has the following file permissions : 0664

参考：
http://php.net/manual/en/function.is-writable.php