Inconsistency in SplFileObject::fwrite $length Parameter Behavior

[SigmaFlame]

Bug Report: Inconsistency in SplFileObject::fwrite $length Parameter Behavior

Description:
The SplFileObject::fwrite method's signature is as follows:

public SplFileObject::fwrite(string $data, int $length = 0): int|false

The issue lies in the $length parameter. Unlike the fwrite function in PHP (which allows $length to be null to write the entire $data string), the SplFileObject::fwrite method does not accept null for $length. This creates inconsistency and forces developers to implement an unnecessary workaround.

Problem:

1. If $length is passed as 0 (the default value), it writes 0 bytes to the file, contrary to the expectation that 0 would mean "write everything" (similar to the fwrite function).
2. To bypass this behavior and write the full $data, one must write conditional logic:

   if (is_null($length)) {
       $written = $this->file->fwrite($data);
   } else {
       $written = $this->file->fwrite($data, $length);
   }

Expected Behavior:
The method should allow $length to be null to indicate that the full $data string should be written, consistent with the fwrite function.

Current Behavior:

• $length = 0 writes 0 bytes, which is counterintuitive and unproductive.
• Passing null for $length throws a type error.

Documentation Reference:
SplFileObject::fwrite documentation

---

Suggested Fix:
Update the method to allow $length to be null, aligning its behavior with the native fwrite function.

[kamil-tekiela]

This is not a documentation issue. You are requesting a change to the language itself.

[nielsdos]

I think this feature request makes a lot of sense.

[cmb69]

Well, I think there is actually a bug; if you omit the second parameter, the method behaves differently as if you pass the second parameter's default value. We should at least change the default parameter (if only in the docs) for the time being.

[nielsdos]

Yeah, it's likely one of those functions that uses the ZEND_NUM_ARGS() trick...

[kamil-tekiela]

I think the parameter should be nullable and have a default null value. Could we make this change in PHP 8.5? If so, I can submit a PR tomorrow.

[nielsdos]

I agree with you, it's a minor BC break so 8.5 seems fine.