When working with PHP, passthru can help with a specific task: runs an operating-system command and streams raw command output directly.
This guide shows what passthru does, how to use it in code, and which details you should check before relying on the result.
What Is passthru in PHP?
Runs an operating-system command and streams raw command output directly.
Usage: The following examples show calls with suitable values. Consult the function parameters described in the examples, especially when optional arguments or extensions are involved.
Example 1: Basic Usage
The first example introduces passthru with a direct PHP expression.
<?php
echo function_exists("passthru") ? "Function available" : "Unavailable";
Observe the value returned or printed by passthru and compare it with the input used in this example.
Example 2: A Different Input or Option
This second example demonstrates another input or condition, so you can compare the behavior with the first example.
<?php
echo ini_get("disable_functions") ?: "No listed disabled functions";
Observe the value returned or printed by passthru and compare it with the input used in this example.
Practical Example
Here is a small scenario illustrating how passthru can fit into application code. Run the example only in an appropriate development environment if it reads files, changes data, starts processes or connects to a service.
<?php
$task = "generate-report"; $allowed = ["generate-report"]; echo in_array($task, $allowed, true) ? "Use a predefined command only" : "Reject";
Observe the value returned or printed by passthru and compare it with the input used in this example.
Important Behavior and Edge Cases
- Core behavior: Runs an operating-system command and streams raw command output directly.
- Important limitation: Never concatenate user-controlled strings into shell commands. Prefer native PHP APIs and avoid exposing raw output to browsers.
- Production use: Check return values and handle failures before acting on the result.
Comparison With Related Functions
| Function or Approach | Difference |
|---|---|
passthru() | Runs an operating-system command and streams raw command output directly. |
exec() | Related approach. Its purpose and return value differ; select it when your task matches that operation. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
Overlooking a special case of passthru(). | Never concatenate user-controlled strings into shell commands. Prefer native PHP APIs and avoid exposing raw output to browsers. |
Using passthru() without checking the outcome. | Handle failures and confirm that the output is suitable for the next step. |
Key Takeaways
- Runs an operating-system command and streams raw command output directly.
- Never concatenate user-controlled strings into shell commands. Prefer native PHP APIs and avoid exposing raw output to browsers.
- Test the function with relevant inputs before using it in production.
Use passthru when its behavior matches the job you need to complete. For dependable results, consider the input data, returned value and limitations shown above.