Month: April 2015

More thoughts on education

“I wish that our current educational approaches put much more emphasis on following one’s curiosity and asking ‘Why?’, rather than on memorization of facts and rote reproduction of processes. We can hardly blame students for not being curious when our educational system doesn’t generally reward that. So, sadly, it is surprising when a student asks ‘Why?'”

–Steven Clarke

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JSON Streaming Output

I recently put together a simple little bit of code to handle streaming large amounts of JSON formatted data to the browser.

In order for you to see any benefit from this, you will need to have the following scenario.

You have a response you’re sending back with some meta information about the response – maybe a response code, or error messages or a single record.

You also have a number of rows to send back as a member of the main JSON object.

These rows don’t all need to be the same object, but you can only have a single variable that you stream.

This allows you to fetch and send a single database row at a time instead of building up a huge response object in memory on the server.

It builds up a response that looks like this (the data in “rows” is streamed one line at a time):

{
    "success":true,
    "rows":
    [
        {"id":1,"random_data":"a6b1e15cc6523e87cb8d5a6a0ea39dbc61842b23"},
        {"id":2,"random_data":"12ae19125e2182294433e835ee8dc7e403154fdd"}
    ]
}


<?
// COPYRIGHT 2015 by TIM GALLGHER (treehousetim@gmail.com)
// https://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() ) );
}

view raw

example.php

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<?
// COPYRIGHT 2015 by TIM GALLGHER (treehousetim@gmail.com)
// https://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 );
}
}
}

view raw

streamBrowserJSON.php

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