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stream_is_local() is a built-in PHP function used to check whether a specified stream points to a file in the local file system. Its function signature is as follows:
<span><span><span class="hljs-keyword">bool</span></span><span> </span><span><span class="hljs-title function_ invoke__">stream_is_local</span></span><span>(</span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$filename</span></span><span>)
</span></span>Parameter: $filename is the filename to be checked. It can be a file path or a URL.
Return value: If the given stream is a local file, it returns true, otherwise false.
This function is often used to distinguish between local files and remote files (such as files accessed via FTP or HTTP), ensuring that file operations are performed only on local files.
Although stream_is_local() is a very straightforward function, different path formats may lead to unexpected results in real-world development. Below are some common pitfalls that developers should be aware of.
When calling stream_is_local(), the path can be a local file system path or a URL. If you pass in a path with a protocol prefix (such as http:// or ftp://), stream_is_local() will check whether the path points to the local file system. If it’s a remote URL, it will return false.
Gotcha: You might mistakenly think that stream_is_local() determines locality solely based on path format, ignoring the protocol part.
Solution: Ensure that the path you pass is a valid local file path, not a remote URL. If it’s a URL, handle it accordingly based on your needs.
<span><span><span class="hljs-variable">$filename</span></span><span> = </span><span><span class="hljs-string">"http://example.com/file.txt"</span></span><span>;
</span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-title function_ invoke__">stream_is_local</span></span><span>(</span><span><span class="hljs-variable">$filename</span></span><span>)) {
</span><span><span class="hljs-comment">// This will return false</span></span><span>
}
</span></span>The PHP stream_is_local() function only returns true if the path points to the local file system. However, if the path format is not as expected—for example, missing a file protocol prefix like file://—it may lead to incorrect results.
Gotcha: If the file path does not explicitly include the file:// protocol, the function may return the wrong result.
Solution: When working with local file paths, it’s best to always explicitly specify the file:// protocol to ensure correct identification.
<span><span><span class="hljs-variable">$localPath</span></span><span> = </span><span><span class="hljs-string">"/var/www/html/test.txt"</span></span><span>; </span><span><span class="hljs-comment">// May return false</span></span><span>
</span><span><span class="hljs-variable">$localPathWithProtocol</span></span><span> = </span><span><span class="hljs-string">"file://<span class="hljs-subst">$localPath</span></span></span><span>"; </span><span><span class="hljs-comment">// More explicit</span></span><span>
</span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-title function_ invoke__">stream_is_local</span></span><span>(</span><span><span class="hljs-variable">$localPathWithProtocol</span></span><span>)) {
</span><span><span class="hljs-comment">// This will return true</span></span><span>
}
</span></span>Different operating systems use different path formats and separators. In particular, Windows uses backslashes (\) as path separators, while Unix-like systems (Linux, macOS) use forward slashes (/). The stream_is_local() function checks paths based on the current OS format, so you need to make sure your path format is correct.
Gotcha: On Windows, paths with backslashes may cause stream_is_local() to fail to recognize them as local files.
Solution: Ensure that path separators match the current operating system, or use the DIRECTORY_SEPARATOR constant on Windows for automatic adaptation.
<span><span><span class="hljs-variable">$path</span></span><span> = </span><span><span class="hljs-string">"C:\\Users\\test\\file.txt"</span></span><span>; </span><span><span class="hljs-comment">// Windows backslash path</span></span><span>
</span><span><span class="hljs-variable">$pathLinux</span></span><span> = </span><span><span class="hljs-string">"/home/user/file.txt"</span></span><span>; </span><span><span class="hljs-comment">// Unix-like forward slash path</span></span><span>
</span></span>The stream_is_local() function handles relative and absolute paths differently. If you pass a relative path, PHP resolves it against the current working directory. This may lead to errors, especially across different execution environments.
Gotcha: Using a relative path may cause stream_is_local() to misjudge the file’s locality, depending on the working directory.
Solution: Always use absolute paths when possible. You can use the realpath() function to convert a relative path into an absolute one.
<span><span><span class="hljs-variable">$relativePath</span></span><span> = </span><span><span class="hljs-string">"./file.txt"</span></span><span>;
</span><span><span class="hljs-variable">$absolutePath</span></span><span> = </span><span><span class="hljs-title function_ invoke__">realpath</span></span><span>(</span><span><span class="hljs-variable">$relativePath</span></span><span>); </span><span><span class="hljs-comment">// Get absolute path</span></span><span>
</span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-title function_ invoke__">stream_is_local</span></span><span>(</span><span><span class="hljs-variable">$absolutePath</span></span><span>)) {
</span><span><span class="hljs-comment">// Correctly determines local file</span></span><span>
}
</span></span>stream_is_local() determines whether a stream path points to a local file, not a directory. If you pass in a directory path instead of a file path, the function will return false. This can be confusing when checking whether a directory is on the local file system.
Gotcha: If the path points to a directory instead of a file, stream_is_local() will return false, which may not be what you expect.
Solution: When using stream_is_local(), make sure the path points to a file, not a directory. To check directories, use other functions such as is_dir().
<span><span><span class="hljs-variable">$dirPath</span></span><span> = </span><span><span class="hljs-string">"/var/www/html"</span></span><span>;
</span><span><span class="hljs-keyword">if</span></span><span> (</span><span><span class="hljs-title function_ invoke__">stream_is_local</span></span><span>(</span><span><span class="hljs-variable">$dirPath</span></span><span>)) {
</span><span><span class="hljs-comment">// This will return false, because it's a directory</span></span><span>
}
</span></span>