When working with PHP in PHP, it helps to understand exactly what readgzfile() does and when the result is useful. This guide uses small examples followed by a practical pattern.
What Is readgzfile() in PHP?
Opens a gzip-compressed file, writes its decompressed content to output, and returns the number of decompressed bytes.
Syntax:
readgzfile(string $filename, int $use_include_path = ...) : int|false
Parameters:
$filename(string) is required.$use_include_path(int) is optional.
Return value: PHP declares int|false for this API in PHP 8.4 where available. For operations that can fail, check errors or exceptions instead of assuming success.
Example 1: Basic Usage
The first example focuses on the operation itself without unrelated application logic.
<?php
$filePath = __DIR__ . "/manual.txt";
$gzipPath = __DIR__ . "/manual.txt.gz";
if (!is_file($gzipPath)) {
throw new RuntimeException("Example file not found");
}
readgzfile($gzipPath);
Opens a gzip-compressed file, writes its decompressed content to output, and returns the number of decompressed bytes. The example demonstrates the API in an isolated teaching script. File paths, permissions and optional extensions may need adapting for a real project.
Example 2: Handling Conditions and Failures
Production code must handle cases where the archive, file, runtime feature, or source path is not available. The following example demonstrates an additional usage pattern.
<?php
$downloadPath = __DIR__ . "/archive.csv.gz";
if (!is_file($downloadPath)) {
throw new RuntimeException("Missing download file");
}
$bytesSent = readgzfile($downloadPath);
if ($bytesSent === false) {
throw new RuntimeException("Streaming failed");
}
Only catch errors you can handle meaningfully. A PHP warning, a false return value, and an exception are not interchangeable; consult the behavior explained above.
Practical Example: Integrating the Operation
This practical variation shows how to place the operation in a larger file or inspection workflow. The paths and names are illustrative rather than server deployment instructions.
<?php
function inspectEnvironment(): void
{
readgzfile($gzipPath);
}
inspectEnvironment();
Do not copy sample paths blindly into production. Validate allowed paths and confirm the appropriate extension and filesystem permissions first.
Important Behavior and Edge Cases
- The function writes file contents to the output stream, so it must not be used on private server-side data.
- Set the correct Content-Type and Content-Disposition before streaming HTTP downloads.
- Untrusted path input must be checked against an allowed directory.
Comparison With Related Functions
| Function or Method | Purpose |
|---|---|
readgzfile | Opens a gzip-compressed file, writes its decompressed content to output, and returns the number of decompressed bytes. |
file_get_contents() | Loads file contents into a string instead of directly streaming them. |
realpath() | Resolves a filesystem path instead of inspecting or changing a PHP setting. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Assuming filesystem state cannot change after a check. | Handle failures from the actual file operation. |
| Passing unchecked user paths into filesystem APIs. | Restrict paths to known directories and validate resolved destinations. |
| Displaying sensitive filesystem configuration to visitors. | Keep diagnostic output in restricted administrative tools. |
Key Takeaways
- Opens a gzip-compressed file, writes its decompressed content to output, and returns the number of decompressed bytes.
- The function writes file contents to the output stream, so it must not be used on private server-side data.
- Set the correct Content-Type and Content-Disposition before streaming HTTP downloads.
readgzfile() is useful when its specific purpose matches your application. Keep the examples focused, respect the restrictions above, and validate real-world inputs rather than relying on the example values.