gently handle memory with ob_start 's callback & StreamableInterface

ob_start.php

 <?php
 // $ php -d memory_limit=6M ob_start.php

 class TempStreamable
 {
     public $fp;

     public function __construct()
     {
         $OneMB = 1 * 1024 * 1024;
         $this->fp = fopen("php://temp/maxmemory:$OneMB", 'r+b');
     }

     public function write($buffer)
     {
         return fwrite($this->fp, $buffer);
     }

     public function getContents()
     {
         return stream_get_contents($this->fp, -1, 0);
     }

 }

 $streamable = new TempStreamable;

 //ob_start(function($buffer) use (&$streamable) {
 //    $streamable->write($buffer);
 //});
 ob_start(function($buffer) use (&$streamable) {
     $streamable->write($buffer);
 }, 1024 * 1024);

 // big big response..
 foreach (range(0, 9) as $i) {
     echo str_repeat($i, 1024 * 1024);
 }

 ob_end_flush();

 echo `ls -la /tmp`; // 10MB temporary file will be created.

 // var_dump($streamable->getContents()); // PHP Fatal error:  Allowed memory size of 6291456 bytes exhausted (tried to allocate 10493952 bytes)

 rewind($streamable->fp); fpassthru($streamable->fp);