In PHP, filter_list() helps with runtime and application data. Returns the registered PHP filtering names supported by the runtime.
What Is filter_list() in PHP?
The function or method has a specific purpose: Returns the registered PHP filtering names supported by the runtime. The following examples show the main call, one additional situation, and an application-style use.
Syntax:
<?php
filter_list() : array
Parameters and Return Value
This API accepts no arguments.
Example 1: Basic Usage
Returns the registered PHP filtering names supported by the runtime.
<?php
$availableFilters = filter_list();
echo count($availableFilters);
This example demonstrates the central operation. The final output depends on the supplied input and, where relevant, the runtime or connected service.
Example 2: Handling a Different Case
<?php
var_dump(in_array("validate_email", filter_list(), true));
The second example focuses on a different input or failure condition, so the behavior can be distinguished from the basic case.
Practical Example
<?php
foreach (filter_list() as $filterName) { echo $filterName . "\n"; }
The practical example demonstrates how the same subject fits into a larger application. Use your own file paths, endpoints and validated inputs rather than copying sample settings directly.
Important Behavior and Edge Cases
- Returns the registered PHP filtering names supported by the runtime.
- Check the return value and exceptions for failure before using the result. If an extension or external system is required, the example only works when that dependency is available.
- Use the documented return type and handle false, null and exceptions according to the specific call.
Comparison With Related Functions
| Approach | Difference |
|---|---|
| filter_list | Returns the registered PHP filtering names supported by the runtime. |
| filter_var | Validates or filters a supplied value directly. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Ignoring errors from filter_list | Check the actual result and handle the expected error path. |
| Using the demonstration unchanged in production | Adapt file paths, configuration, authentication and permission rules to the application. |
| Treating input or returned data as trusted | Apply validation at input boundaries and context-aware escaping at output boundaries. |
Key Takeaways
- Returns the registered PHP filtering names supported by the runtime.
- Check the return value and exceptions for failure before using the result. If an extension or external system is required, the example only works when that dependency is available.
- Use the documented return type and handle false, null and exceptions according to the specific call.
Returns the registered PHP filtering names supported by the runtime. Use this approach when its capabilities and constraints match the application. Handle invalid data, failure conditions and resource cleanup explicitly.