highlight_file() Function is one of the PHP operations used in filesystem and stream workflows. Returns or prints syntax-highlighted PHP source from a file. The examples below show what it does and how to handle its result.
What Is highlight_file() Function?
Returns or prints syntax-highlighted PHP source from a file.
Its syntax is:
highlight_file(string $filename, bool $return = false)
The parameters are:
string $filename— The source or destination filesystem path.bool $return = false— When true, returns highlighted source HTML instead of printing it immediately.
Return value: The declared return type is string|bool. Never expose application source or secrets to unauthenticated users.
Important: Never expose application source or secrets to unauthenticated users.
Example 1: Basic Usage
The basic example focuses on the behavior of highlight_file() Function: returns or prints syntax-highlighted PHP source from a file. Inputs are defined locally or shown as application-controlled paths.
<?php
$highlightedSource = highlight_file(__FILE__, true);
if ($highlightedSource !== false) { echo strlen($highlightedSource); }
The displayed value, file content or return status depends on the input and surrounding environment. Results involving local paths, identifiers or generated files are not fixed values.
Example 2: A Different Use Case
This second example illustrates another input or execution condition for highlight_file() Function. Notice the different checks, arguments, or output handling.
<?php
$sourcePath = __FILE__;
if (is_file($sourcePath)) { $htmlSource = highlight_file($sourcePath, true); echo $htmlSource === false ? "Failed" : "Highlighted"; }
This variation matters because never expose application source or secrets to unauthenticated users.
Practical Example: Using the Operation in an Application
The following example demonstrates how highlight_file() Function fits into a more complete file or archive workflow, including inputs and appropriate checks.
<?php
$sourcePath = __DIR__ . "/example.php";
if (is_file($sourcePath)) { $highlighted = highlight_file($sourcePath, true); echo $highlighted === false ? "Failed" : "Source highlighted"; }
The operation shown is an illustrative script. Adapt the filenames, required permissions, and error handling to your own controlled application environment before running it.
Important Behavior and Edge Cases
- Function behavior: Returns or prints syntax-highlighted PHP source from a file.
- Limitation: Never expose application source or secrets to unauthenticated users.
Comparison With Related Functions
| Function or Method | Difference |
|---|---|
highlight_file() Function | Returns or prints syntax-highlighted PHP source from a file. |
highlight_string() | Highlights a string of PHP source instead of reading a source file. |
Use highlight_file() Function for the specific behavior described above. The related operation, highlight_string(), serves a different purpose; do not substitute it unless that different behavior is intended.
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Assuming this operation has the same behavior on every file or environment. | Never expose application source or secrets to unauthenticated users. Check prerequisites and return values before using the result. |
| Treating highlight_string() as an interchangeable replacement for highlight_file() Function. | Highlights a string of PHP source instead of reading a source file. |
Key Takeaways
- Returns or prints syntax-highlighted PHP source from a file.
- Never expose application source or secrets to unauthenticated users.
- Related operation: highlight_string() — Highlights a string of PHP source instead of reading a source file.
highlight_file() Function is useful when its specific behavior matches your application requirement. Keep paths controlled, check failures, and handle environment-dependent operations deliberately.