Streaming JSON to browser using PHP for large record sets of repeating rows

example.php

<?
// COPYRIGHT 2015 by TIM GALLGHER (treehousetim@gmail.com)
// http://treehousetim.com/2015/04/08/new-json-streaming-output-code/

//The MIT License (MIT)
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

// Example:
// create your response
// this can be as complex as you want, but it must have single array of records to be effective.
// it sends in 3 stages.
// stage 1: send the entire response object except for the rows
// stage 2: send the rows, streaming one row at a time
// stage 3: send the closing JSON syntax
// if you bundle all your data into a single row, this approach will not yield any benefit
// the primary point of this file
include( 'streamBrowserJSON.php' );
$response = new stdClass();
$response->success = true;
$response->rows = array();

// start example
outStreamJSON::getInstance()
	->createTemplate( $response, 'rows' )

	// adds ")]}',\n" by default, or pass in a value of your own
	->csrfHeader()

	// only one line handler is used at a time.
	// pass a standard callback that can be used with call_user_func
	->addLineHandler( 'createRow' )

	// the syntax if you're using 
	//->addLineHandler( array( $this, 'getRow' ) )
	->addOutput()
	->render();

// an example row handling function
function createRow()
{
	static $cnt = 0;
	if( $cnt++ > 10000 )
	{
		return false;
	}
	// create a bunch of example data
	return (object)array( 'id' => $cnt, 'random_data' =>  sha1( rand() ) . sha1( rand() ) . sha1( rand() ) . sha1( rand() ) . sha1( rand() ) . sha1( rand() ) . sha1( rand() ) . sha1(rand() ) . sha1(rand() ) );
}

streamBrowserJSON.php

<?

// COPYRIGHT 2015 by TIM GALLGHER (treehousetim@gmail.com)
// http://treehousetim.com/2015/04/08/new-json-streaming-output-code/

//The MIT License (MIT)
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

// the output class - allows for outputting to mutiple streams at once - i.e. file logging and browser
class outStreamJSONOutput
{
	public $stream;
	protected $filename;

	public function __construct( $filename = null )
	{
		if ( $filename == null )
		{
			$filename = 'php://output';
		}

		$this->stream = new SplFileObject( $filename, 'w' );
		$this->filename = $filename;
	}
	//------------------------------------------------------------------------------
	public function out( $out )
	{
		$this->stream->fwrite( $out );
	}
	//------------------------------------------------------------------------------
	public function encodeRow( $data )
	{
		static $first = true;
		$line = ($first?'':',') . json_encode( $data );
		$this->out( $line );
		$first = false;
	}
}

// the main class
class outStreamJSON
{
	protected $_templateTop;
	protected $_templateBottom;
	protected $_csrfHeader = '';
	protected $_outputs = array();
	protected $_lineCb;

	public static function getInstance()
	{
		return new outStreamJSON();
	}
	//------------------------------------------------------------------------------
	public function csrfHeader( $header = ")]}',\n" )
	{
		$this->_csrfHeader = $header;
		return $this;
	}
	//------------------------------------------------------------------------------
	public function createTemplate( $obj, $arrName )
	{
		unset( $obj->{$arrName} );
		$obj->{$arrName} = array();
		$template = json_encode( $obj );
		$splitter = '"' . $arrName . '":[';
		$parts = explode( $splitter, $template );
		$parts[0] .= $splitter;

		$this->_templateTop = $parts[0];
		$this->_templateBottom = $parts[1];

		return $this;
	}
	//------------------------------------------------------------------------
	public function addOutput( $filename = null )
	{
		$this->_outputs[] = new outStreamJSONOutput( $filename );

		return $this;
	}
	//------------------------------------------------------------------------------
	public function addLineHandler( $cb )
	{
		$this->_lineCb = $cb;

		return $this;
	}
	//------------------------------------------------------------------------
	public function render()
	{
		foreach( $this->_outputs as $output )
		{
			$output->out( $this->_csrfHeader . $this->_templateTop );
		}

		while( $line = call_user_func( $this->_lineCb ) )
		{
			foreach( $this->_outputs as $output )
			{
				$output->encodeRow( $line );
			}
		}

		foreach( $this->_outputs as $output )
		{
			$output->out( $this->_templateBottom );
		}
	}
}