PHP stream_bucket_prepend() Function: Usage and Examples

In PHP, stream_bucket_prepend() is useful when your application needs a specific operation rather than manually reproducing it. Adds a bucket to the beginning of a bucket brigade inside a custom stream filter.

Stream functions work with PHP stream resources, wrappers, contexts or custom filters. Not every wrapper supports every operation.

What Is stream_bucket_prepend() in PHP?

Adds a bucket to the beginning of a bucket brigade inside a custom stream filter.

Signature:

stream_bucket_prepend($brigade, StreamBucket $bucket): void

Parameters:

$brigade — The stream filter bucket brigade being modified.
$bucket — A stream data bucket provided by the filter runtime.

Return value: void.

Example 1: Basic Usage

This first example shows the method or function in a minimal context. For environment-dependent operations, adapt the required path, stream or connection before running it.

<?php

class DemoFilter extends php_user_filter {
    public function filter($input, $output, &$consumed, bool $closing): int {
        while ($incomingBucket = stream_bucket_make_writeable($input)) {
            $consumed += $incomingBucket->datalen;
            stream_bucket_prepend($output, $incomingBucket);
        }
        return PSFS_PASS_ON;
    }
}
stream_filter_register("guide.prepend", DemoFilter::class);
$stream = fopen("php://temp", "w+");
stream_filter_append($stream, "guide.prepend", STREAM_FILTER_WRITE);
fwrite($stream, "Hello");
rewind($stream);
echo stream_get_contents($stream);
fclose($stream);

The important operation is stream_bucket_prepend(). Adds a bucket to the beginning of a bucket brigade inside a custom stream filter.

Example 2: Another Input or Scenario

The next example changes the input or surrounding context to show how the operation behaves in a second situation.

<?php

class DemoFilter extends php_user_filter {
    public function filter($input, $output, &$consumed, bool $closing): int {
        while ($incomingBucket = stream_bucket_make_writeable($input)) {
            $consumed += $incomingBucket->datalen;
            stream_bucket_prepend($output, $incomingBucket);
        }
        return PSFS_PASS_ON;
    }
}
stream_filter_register("guide.prepend", DemoFilter::class);
$stream = fopen("php://temp", "w+");
stream_filter_append($stream, "guide.prepend", STREAM_FILTER_WRITE);
fwrite($stream, "Second item");
rewind($stream);
echo stream_get_contents($stream);
fclose($stream);

Compare the inputs and the handling of the return value with the first example. Avoid assuming that filesystem paths, resource states or binary bytes are interchangeable.

Practical Example: Applying the Operation

This example illustrates how the operation fits into a small application workflow. Paths, streams and secrets must be created or provided securely by the calling application.

<?php

class DemoFilter extends php_user_filter {
    public function filter($input, $output, &$consumed, bool $closing): int {
        while ($incomingBucket = stream_bucket_make_writeable($input)) {
            $consumed += $incomingBucket->datalen;
            stream_bucket_prepend($output, $incomingBucket);
        }
        return PSFS_PASS_ON;
    }
}
stream_filter_register("guide.prepend", DemoFilter::class);
$stream = fopen("php://temp", "w+");
stream_filter_append($stream, "guide.prepend", STREAM_FILTER_WRITE);
fwrite($stream, "Report value");
rewind($stream);
echo stream_get_contents($stream);
fclose($stream);

Practical note: Adds a bucket to the beginning of a bucket brigade inside a custom stream filter.

Important Behavior and Edge Cases

Adds a bucket to the beginning of a bucket brigade inside a custom stream filter.
Check failure values and exceptions; do not assume every environment supports the same stream wrapper, extension or filesystem capability.
When handling paths, streams or external input, validate inputs before using results and release resources after use.

Comparison With Related Functions

Function or Method	Behavior
`stream_bucket_prepend()`	prepends the bucket to the brigade.
`stream_bucket_append()`	places it at the end.

Common Beginner Mistakes

Mistake	Correct Approach
Assuming `stream_bucket_prepend()` can be used without its required setup	Provide the correct file, stream, state, key or object before calling it; Adds a bucket to the beginning of a bucket brigade inside a custom stream filter.
Using bucket operations outside a filter callback	Stream bucket APIs are intended for php_user_filter subclasses and their provided brigades.
Forgetting consumed byte counts or filter order	Account for consumed data and test read/write filter ordering before deployment.

Key Takeaways

stream_bucket_prepend() adds a bucket to the beginning of a bucket brigade inside a custom stream filter.
Use appropriate input types and verify results before continuing.
Prefer specialized, safer APIs when the operation concerns untrusted input, encryption or network traffic.

In summary: Adds a bucket to the beginning of a bucket brigade inside a custom stream filter. Build in error handling and use this function where its specific behavior matches the application requirements.