When working with PHP, you may need to retrieve the byte position and length of the next regex match. This guide explains the operation, shows what its arguments mean, and uses three separate examples to make the result easier to understand.
mb_ereg_search_pos: Positions are byte offsets in the underlying search string, not always Unicode character positions.
What Is mb_ereg_search_pos in PHP?
Retrieve the byte position and length of the next regex match. Positions are byte offsets in the underlying search string, not always Unicode character positions.
Syntax:
mb_ereg_search_pos(?string $pattern = null, ?string $options = null): array|false
Parameters and return value: The signature above identifies the arguments and return type where the API has a single call. For topic guides, follow the sequence of calls in the examples. Always distinguish a returned value from an object or variable modified by reference.
Important: Always compare against false strictly and do not confuse byte positions with character indexes.
Example 1: Basic Usage
This example introduces the operation with a short and predictable input.
<?php
mb_ereg_search_init("Order 42");
print_r(mb_ereg_search_pos("[0-9]+"));
The code focuses on the main operation. Positions are byte offsets in the underlying search string, not always Unicode character positions.
Example 2: Another Case
Now compare a different input, locale, date, or option to see another part of the behavior.
<?php
mb_ereg_search_init("No digits");
var_dump(mb_ereg_search_pos("[0-9]+"));
What changes? Always compare against false strictly and do not confuse byte positions with character indexes.
Practical Example: Applying It in an Application
Use the following separate example as a starting point for a small application task. Check any extension or environment requirements below before running it.
<?php
$record = "User 12, item 93";
mb_ereg_search_init($record);
while (($position = mb_ereg_search_pos("[0-9]+")) !== false) {
print_r($position);
}
The practical example demonstrates how to apply this operation to multiple values, a reusable task, or a validated input. Positions are byte offsets in the underlying search string, not always Unicode character positions.
Important Behavior and Edge Cases
- Core behavior: Positions are byte offsets in the underlying search string, not always Unicode character positions.
- Inputs and results: Always compare against false strictly and do not confuse byte positions with character indexes.
- Alternatives: mb_ereg_search_regs() returns matched text rather than a byte-position pair.
- Compatibility: mbstring is required for mb_* functions.
Comparison With Related Functions
| Function or Approach | When to Use It |
|---|---|
mb_ereg_search_pos | Retrieve the byte position and length of the next regex match. |
| Related PHP approach | mb_ereg_search_regs() returns matched text rather than a byte-position pair. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Using an incorrect input or option | Always compare against false strictly and do not confuse byte positions with character indexes. |
| Confusing this API with a related operation | mb_ereg_search_regs() returns matched text rather than a byte-position pair. |
| Assuming output is identical across environments | Check return values and required extensions or versions. mbstring is required for mb_* functions. |
Key Takeaways
- mb_ereg_search_pos helps you retrieve the byte position and length of the next regex match.
- Positions are byte offsets in the underlying search string, not always Unicode character positions.
- Always compare against false strictly and do not confuse byte positions with character indexes.
Use mb_ereg_search_pos when you need to retrieve the byte position and length of the next regex match. Start with the first example, compare the second, and adapt the practical example to your inputs. Confirm the return value and environment requirements before adding it to production code.