I find this concept fascinating and plan to investigate further down this road.
Archive for the ‘PHP’ Category
If you’re ever in a situation where something is only happening intermittently, and only on a live server, and only while it’s under load… Lets say its not generating any error_log or stderr output, and you cant run it manually to reproduce… (we’ve all been in this situation) How do you get any debugging output at all?
Step 1: add this to the top of your entry point php file
if ( $_SERVER['REMOTE_ADDR'] == '127.0.0.1' ) { error_log( ' :: ' . getmypid() ); sleep( 10 ); }
Step 2: use curl on the localhost to make the request
Step 3: (this assumes your error log is /tmp/php-error-output) run the following command in a second (root) terminal window
strace -p $(tail -n 1000 /tmp/php-error-output | grep ' :: ' | tail -n 1 | sed -r s/'^.+ :: '//g) -s 10240 2>&1
Good luck…
When working with user provided images in PHP you run into a problem. Lets say that you want to generate thumbnails of uploaded JPEGs for users. This is a fairly common use case where you would employ PHP and GD (the most prevalent php image extension.) But when you generate the new, smaller, image what quality setting do you use? If your quality setting is too low then the image is distorted unacceptably. Likewise if your quality setting is too high then you produce a dimensionally smaller image with a larger size in bytes than the original. So what do you do when you want to satisfy all cases? Well the obvious answer is that you should use the same JPEG quality setting that the image had when it was uploading. Now… Using PHP and GD tell me how you accomplish this.
Go ahead
I’ll wait
You can’t, can you? If you’re really sneaky you might be thinking about just pulling the data out of the binary stream, and if you’re a linux nut you’re probably sitting there muttering “just use identify (a la imagemagick)”. Of course if you try that under heavy traffic you’ll soon discover that it kills your servers. Just for reference I’ll share that code with you (not everyone is serving 2g/sec in dynamic image traffic after all). We already have the binary data in ram in the $rval variable, in case you were curious.
// define how we will deal with stdin, stdout, and stderr $descriptorspec = array( 0 => array( "pipe", "r" ), 1 => array( "pipe", "w" ), 2 => array( "pipe", "a" ) ); // run identify, -verbose required, - means read file from stdin $process = proc_open( IDENTIFY . ' -verbose -', $descriptorspec, $pipes ); if ( false !== $process ) { // pipe the image data through it to its stdin fwrite( $pipes[0], $rval ); // close stdin to allow identify to process fclose( $pipes[0] ); // read the results of the program execution $results = stream_get_contents($pipes[1]); // clean up open file handles fclose( $pipes[1] ); fclose( $pipes[2] ); // Unix return value of 0 means success if ( 0 == proc_close($process) ) { // pull out the image quality from identify output if ( preg_match( '#Quality: ([0-9]+)[^0-9]#', $results, $m ) ) $origin_quality = intval($m[1]); // detect when something goes wrong above if ( $origin_quality == 0 ) $origin_quality = 100; } }
So, since this consumes too much of our available resources (especially ram and cpu usage since identify fully decompresses and reads the image into a raw state for processing… hundreds of MB of ram, which you can limit but then it becomes unbearably slow…) that’s out. What now? If you’re really extra sneaky you’re thinking that you should be able to read the setting out of the binary data… there should be a header after all, right? Well… Yes there is a header but “quality” is not a “setting” its more a measure of how compressed the image is… which isn’t exactly recorded either… at least… not as an integer value. The compression matrix used to preform JPEGs lossy compression *IS* stored in a header.. and it turns out this is what the ImageMagick code uses to give us that quality setting. So I set out to reproduce this in PHP.
I know… I’m a masochist.
Thanks to some serious google-fu (and possibly a note in a php online doc manual relating to IPC, I don’t remember which of the two led me to the package first) I found that there’s already some code out there which deals with the nasty bits of reading raw JPEG headers (though not doing what I want with the header that I want) in the PHP JPEG Metadata Toolkit And the instructions for evaluating the header we can then pull is in the ImageMagick source code (coders/jpeg.c)
When we put the two together and modify it a bit to suite our needs (i.e. reading from the in-memory buffer, pulling just the right header from the jpeg file, etc) we get this code… and finally the ability to call $quality = get_jpeg_quality( $rval ); In my test (yea just one or two… very scientific like), this over 100 times faster than using the proc_open and executable method, uses less ram (a lot lot lot lot lot less ram) and generally just doesn’t suck as much.
< ?php function get_jpeg_header_data( &$buff, $want=null ) { $data = buffer_read( $buff, 2, true ); // Read the first two characters // Check that the first two characters are 0xFF 0xDA (SOI - Start of image) if ( $data != "\xFF\xD8" ) { // No SOI (FF D8) at start of file - This probably isn't a JPEG file - close file and return; return false; } $data = buffer_read( $buff, 2 ); // Read the third character // Check that the third character is 0xFF (Start of first segment header) if ( $data{0} != "\xFF" ) { // NO FF found - close file and return - JPEG is probably corrupted return false; } // Cycle through the file until, one of: // 1) an EOI (End of image) marker is hit, // 2) we have hit the compressed image data (no more headers are allowed after data) // 3) or end of file is hit $hit_compressed_image_data = FALSE; while ( ( $data{1} != "\xD9" ) && ( !$hit_compressed_image_data) && ( $data != '' ) ) { // Found a segment to look at. // Check that the segment marker is not a Restart marker - restart markers don't have size or data after them if ( ( ord($data{1}) < 0xD0 ) || ( ord($data{1}) > 0xD7 ) ) { // Segment isn't a Restart marker $sizestr = buffer_read( $buff, 2 ); // Read the next two bytes (size) $decodedsize = unpack ("nsize", $sizestr); // convert the size bytes to an integer // Read the segment data with length indicated by the previously read size $segdata = buffer_read( $buff, $decodedsize['size'] - 2 ); // Store the segment information in the output array if ( !$want || $want == ord($data{1}) ) { $headerdata[] = (object)array( "SegType" => ord($data{1}), "SegName" => $GLOBALS[ "JPEG_Segment_Names" ][ ord($data{1}) ], "SegDesc" => $GLOBALS[ "JPEG_Segment_Descriptions" ][ ord($data{1}) ], "SegData" => $segdata ); } } // If this is a SOS (Start Of Scan) segment, then there is no more header data - the compressed image data follows if ( $data{1} == "\xDA" ) { $hit_compressed_image_data = true; } else { // Not an SOS - Read the next two bytes - should be the segment marker for the next segment $data = buffer_read( $buff, 2 ); // Check that the first byte of the two is 0xFF as it should be for a marker if ( $data{0} != "\xFF" ) { // NO FF found - close file and return - JPEG is probably corrupted return false; } } } return $headerdata; } function buffer_read( &$buff, $len, $new=false ) { static $pointer = 0; if ( $new ) $pointer = 0; if ( $pointer + $len > strlen( $buff ) ) { $len = strlen( $buff ) - $pointer; if ( $len < 1 ) return null; } $data = substr( $buff, $pointer, $len ); $pointer += $len; return $data; } // The names of the JPEG segment markers, indexed by their marker number $GLOBALS[ "JPEG_Segment_Names" ] = array( 0xC0 => "SOF0", 0xC1 => "SOF1", 0xC2 => "SOF2", 0xC3 => "SOF4", 0xC5 => "SOF5", 0xC6 => "SOF6", 0xC7 => "SOF7", 0xC8 => "JPG", 0xC9 => "SOF9", 0xCA => "SOF10", 0xCB => "SOF11", 0xCD => "SOF13", 0xCE => "SOF14", 0xCF => "SOF15", 0xC4 => "DHT", 0xCC => "DAC", 0xD0 => "RST0", 0xD1 => "RST1", 0xD2 => "RST2", 0xD3 => "RST3", 0xD4 => "RST4", 0xD5 => "RST5", 0xD6 => "RST6", 0xD7 => "RST7", 0xD8 => "SOI", 0xD9 => "EOI", 0xDA => "SOS", 0xDB => "DQT", 0xDC => "DNL", 0xDD => "DRI", 0xDE => "DHP", 0xDF => "EXP", 0xE0 => "APP0", 0xE1 => "APP1", 0xE2 => "APP2", 0xE3 => "APP3", 0xE4 => "APP4", 0xE5 => "APP5", 0xE6 => "APP6", 0xE7 => "APP7", 0xE8 => "APP8", 0xE9 => "APP9", 0xEA => "APP10", 0xEB => "APP11", 0xEC => "APP12", 0xED => "APP13", 0xEE => "APP14", 0xEF => "APP15", 0xF0 => "JPG0", 0xF1 => "JPG1", 0xF2 => "JPG2", 0xF3 => "JPG3", 0xF4 => "JPG4", 0xF5 => "JPG5", 0xF6 => "JPG6", 0xF7 => "JPG7", 0xF8 => "JPG8", 0xF9 => "JPG9", 0xFA => "JPG10", 0xFB => "JPG11", 0xFC => "JPG12", 0xFD => "JPG13", 0xFE => "COM", 0x01 => "TEM", 0x02 => "RES", ); // The descriptions of the JPEG segment markers, indexed by their marker number $GLOBALS[ "JPEG_Segment_Descriptions" ] = array( /* JIF Marker byte pairs in JPEG Interchange Format sequence */ 0xC0 => "Start Of Frame (SOF) Huffman - Baseline DCT", 0xC1 => "Start Of Frame (SOF) Huffman - Extended sequential DCT", 0xC2 => "Start Of Frame Huffman - Progressive DCT (SOF2)", 0xC3 => "Start Of Frame Huffman - Spatial (sequential) lossless (SOF3)", 0xC5 => "Start Of Frame Huffman - Differential sequential DCT (SOF5)", 0xC6 => "Start Of Frame Huffman - Differential progressive DCT (SOF6)", 0xC7 => "Start Of Frame Huffman - Differential spatial (SOF7)", 0xC8 => "Start Of Frame Arithmetic - Reserved for JPEG extensions (JPG)", 0xC9 => "Start Of Frame Arithmetic - Extended sequential DCT (SOF9)", 0xCA => "Start Of Frame Arithmetic - Progressive DCT (SOF10)", 0xCB => "Start Of Frame Arithmetic - Spatial (sequential) lossless (SOF11)", 0xCD => "Start Of Frame Arithmetic - Differential sequential DCT (SOF13)", 0xCE => "Start Of Frame Arithmetic - Differential progressive DCT (SOF14)", 0xCF => "Start Of Frame Arithmetic - Differential spatial (SOF15)", 0xC4 => "Define Huffman Table(s) (DHT)", 0xCC => "Define Arithmetic coding conditioning(s) (DAC)", 0xD0 => "Restart with modulo 8 count 0 (RST0)", 0xD1 => "Restart with modulo 8 count 1 (RST1)", 0xD2 => "Restart with modulo 8 count 2 (RST2)", 0xD3 => "Restart with modulo 8 count 3 (RST3)", 0xD4 => "Restart with modulo 8 count 4 (RST4)", 0xD5 => "Restart with modulo 8 count 5 (RST5)", 0xD6 => "Restart with modulo 8 count 6 (RST6)", 0xD7 => "Restart with modulo 8 count 7 (RST7)", 0xD8 => "Start of Image (SOI)", 0xD9 => "End of Image (EOI)", 0xDA => "Start of Scan (SOS)", 0xDB => "Define quantization Table(s) (DQT)", 0xDC => "Define Number of Lines (DNL)", 0xDD => "Define Restart Interval (DRI)", 0xDE => "Define Hierarchical progression (DHP)", 0xDF => "Expand Reference Component(s) (EXP)", 0xE0 => "Application Field 0 (APP0) - usually JFIF or JFXX", 0xE1 => "Application Field 1 (APP1) - usually EXIF or XMP/RDF", 0xE2 => "Application Field 2 (APP2) - usually Flashpix", 0xE3 => "Application Field 3 (APP3)", 0xE4 => "Application Field 4 (APP4)", 0xE5 => "Application Field 5 (APP5)", 0xE6 => "Application Field 6 (APP6)", 0xE7 => "Application Field 7 (APP7)", 0xE8 => "Application Field 8 (APP8)", 0xE9 => "Application Field 9 (APP9)", 0xEA => "Application Field 10 (APP10)", 0xEB => "Application Field 11 (APP11)", 0xEC => "Application Field 12 (APP12) - usually [picture info]", 0xED => "Application Field 13 (APP13) - usually photoshop IRB / IPTC", 0xEE => "Application Field 14 (APP14)", 0xEF => "Application Field 15 (APP15)", 0xF0 => "Reserved for JPEG extensions (JPG0)", 0xF1 => "Reserved for JPEG extensions (JPG1)", 0xF2 => "Reserved for JPEG extensions (JPG2)", 0xF3 => "Reserved for JPEG extensions (JPG3)", 0xF4 => "Reserved for JPEG extensions (JPG4)", 0xF5 => "Reserved for JPEG extensions (JPG5)", 0xF6 => "Reserved for JPEG extensions (JPG6)", 0xF7 => "Reserved for JPEG extensions (JPG7)", 0xF8 => "Reserved for JPEG extensions (JPG8)", 0xF9 => "Reserved for JPEG extensions (JPG9)", 0xFA => "Reserved for JPEG extensions (JPG10)", 0xFB => "Reserved for JPEG extensions (JPG11)", 0xFC => "Reserved for JPEG extensions (JPG12)", 0xFD => "Reserved for JPEG extensions (JPG13)", 0xFE => "Comment (COM)", 0x01 => "For temp private use arith code (TEM)", 0x02 => "Reserved (RES)", ); /** * Most of this function is taken directly from the source code for imagemagick * and how it handles identify -verbose $filename to present you with a Quality * number. This number should be considered approximate. It's essentially * based upon the numbers used to perform compression on the original image * data... * * See: http://www.obrador.com/essentialjpeg/headerinfo.htm * See: http://www.impulseadventure.com/photo/jpeg-quantization.html * See: http://www.impulseadventure.com/photo/jpeg-huffman-coding.html */ function get_jpeg_quality( &$buff ) { $tables = array( 'multi' => array( 'hash' => array( 1020, 1015, 932, 848, 780, 735, 702, 679, 660, 645, 632, 623, 613, 607, 600, 594, 589, 585, 581, 571, 555, 542, 529, 514, 494, 474, 457, 439, 424, 410, 397, 386, 373, 364, 351, 341, 334, 324, 317, 309, 299, 294, 287, 279, 274, 267, 262, 257, 251, 247, 243, 237, 232, 227, 222, 217, 213, 207, 202, 198, 192, 188, 183, 177, 173, 168, 163, 157, 153, 148, 143, 139, 132, 128, 125, 119, 115, 108, 104, 99, 94, 90, 84, 79, 74, 70, 64, 59, 55, 49, 45, 40, 34, 30, 25, 20, 15, 11, 6, 4, 0 ), // hash 'sums' => array ( 32640, 32635, 32266, 31495, 30665, 29804, 29146, 28599, 28104, 27670, 27225, 26725, 26210, 25716, 25240, 24789, 24373, 23946, 23572, 22846, 21801, 20842, 19949, 19121, 18386, 17651, 16998, 16349, 15800, 15247, 14783, 14321, 13859, 13535, 13081, 12702, 12423, 12056, 11779, 11513, 11135, 10955, 10676, 10392, 10208, 9928, 9747, 9564, 9369, 9193, 9017, 8822, 8639, 8458, 8270, 8084, 7896, 7710, 7527, 7347, 7156, 6977, 6788, 6607, 6422, 6236, 6054, 5867, 5684, 5495, 5305, 5128, 4945, 4751, 4638, 4442, 4248, 4065, 3888, 3698, 3509, 3326, 3139, 2957, 2775, 2586, 2405, 2216, 2037, 1846, 1666, 1483, 1297, 1109, 927, 735, 554, 375, 201, 128, 0 ), // sums ), // multi 'single' => array( 'hash' => array( 510, 505, 422, 380, 355, 338, 326, 318, 311, 305, 300, 297, 293, 291, 288, 286, 284, 283, 281, 280, 279, 278, 277, 273, 262, 251, 243, 233, 225, 218, 211, 205, 198, 193, 186, 181, 177, 172, 168, 164, 158, 156, 152, 148, 145, 142, 139, 136, 133, 131, 129, 126, 123, 120, 118, 115, 113, 110, 107, 105, 102, 100, 97, 94, 92, 89, 87, 83, 81, 79, 76, 74, 70, 68, 66, 63, 61, 57, 55, 52, 50, 48, 44, 42, 39, 37, 34, 31, 29, 26, 24, 21, 18, 16, 13, 11, 8, 6, 3, 2, 0 ), // hash 'sums' => array( 16320, 16315, 15946, 15277, 14655, 14073, 13623, 13230, 12859, 12560, 12240, 11861, 11456, 11081, 10714, 10360, 10027, 9679, 9368, 9056, 8680, 8331, 7995, 7668, 7376, 7084, 6823, 6562, 6345, 6125, 5939, 5756, 5571, 5421, 5240, 5086, 4976, 4829, 4719, 4616, 4463, 4393, 4280, 4166, 4092, 3980, 3909, 3835, 3755, 3688, 3621, 3541, 3467, 3396, 3323, 3247, 3170, 3096, 3021, 2952, 2874, 2804, 2727, 2657, 2583, 2509, 2437, 2362, 2290, 2211, 2136, 2068, 1996, 1915, 1858, 1773, 1692, 1620, 1552, 1477, 1398, 1326, 1251, 1179, 1109, 1031, 961, 884, 814, 736, 667, 592, 518, 441, 369, 292, 221, 151, 86, 64, 0 ), // sums ), // single ); // tables $headers = get_jpeg_header_data( $buff, 0xDB ); if ( !is_array( $headers ) || !count( $headers ) ) return 100; $header = $headers[0]; $quality = 0; if ( strlen($header->SegData) > 128 ) { $entry = array( 0 => array(), 1 => array() ); foreach ( str_split( substr( $header->SegData, 1, 64) ) as $chr ) $entry[0][] = ord($chr); foreach ( str_split( substr( $header->SegData, -64) ) as $chr ) $entry[1][] = ord($chr); $sum = array_sum( $entry[0] ) + array_sum( $entry[1] ); $qvalue = $entry[0][2] + $entry[0][53] + $entry[1][0] + $entry[1][63]; $table = "multi"; } else if ( strlen($header->SegData) > 64 ) { $entry = array( 0 => array() ); foreach ( str_split( substr( $header->SegData, 1, 64) ) as $chr ) $entry[0][] = ord($chr); $sum = array_sum( $entry[0] ); $qvalue = $entry[0][2] + $entry[0][53]; $table = "single"; } else { return 100; // go with a safe value } for( $i = 0; $i < 100; $i++ ) { if ( ( $qvalue < $tables[$table]['hash'][$i] ) && ( $sum < $tables[$table]['sums'][$i] ) ) continue; // error_log( "$table >> $qvalue && $sum >> " . ( $i + 1 ) ); return $i + 1; } return 100; // go with a safe value }
Right… serious suckage. Which is why I’m sharing it here so that you don’t have to go through all that trouble. You can just steal my stolen code. Aren’t GPL compatible licenses fun?
Ok, finally, you… in the back… stop jumping up and down screaming about the Imagick PECL extension… In my testing getCompressionQuality() didnt work and getImageCompression() was unavailable (though I hear there is a newer version of the extension now… YMMV)
Don’t you hate that… When it’s 2:00am… and you really should be in bed… But your mind has hold of a problem, and wont let it go. I have a project where it would be really handy for a process to be able to lock (arbitrary string identifier) and for another process to be able to check whether (arbitrary string identifier) is still locked. And the processes that do the locking can die… so the lock really needs to expire when they do. I could use MySQLs get_lock but I’m already abusing the hell out of that for more distributed things (and since you cannot have more than one mysql named lock at a time per connection, i don’t think it would work here…) in the originating processes, and these locks are machine wide, not network wide…
I don’t like flock because you have to actually create a file to try and lock it leaving race conditions and the possibility of orphaned files on the file system which just sucks… I thought about Memcached but I really need something that can be held open for long periods of inactivity and released if the client dies which precludes the infinite and the timed method of memcached value storage…
After some searching I found old — Open Lock Daemon which looked like a super good fit… Until I dug into the communication protocol… What a nightmare for wanting to lock a string… srsly. So not being able to find anything (and apparently not being able to sleep until I had a satisfactory answer) I decided to write one. In PHP, naturally. Weighing in at 180 lines I think it’s a pretty acceptable/workable first pass.
[ edit: code available here ]
Recently I was troubleshooting some inefficiencies with the jobs systems locking and fetching queries at work. Like a good little boy I, originally, came up with one index which satisfied all the queries that I needed to run against this particular critical table.
(`completed`,`heartbeat`,`priority`,`datacenter`,`worker`) -- datetime,datetime,tinyint,varchar(16),varchar(255)
the query looked like this:
SELECT `id`,GET_LOCK(CONCAT('foo_',`id`),0) as mylock FROM `foo_jobs` WHERE `completed` = '0000-00-00 00:00:00' AND `worker` = '' AND `dirty` = 0 AND IS_FREE_LOCK(CONCAT('foo_',`id`)) = 1 AND `priority` = '0' LIMIT 1
This worked really well as long as the number of jobs in the table remained small.. But there was an event horizon of sorts… where after a certain number of rows (say 10k-25k) the query above took so long to get rows that the system could no longer catch up, but would fall invariably behind… Apparently, the problem was that there was too much data in the key. Because the requirements for these queries had changed slightly (due to other scaling improvements) I was able to simplify and break the indexes into parts which vastly outperform the previous index.
KEY `get_a_job` (`priority`,`workerpid`) -- tinyint, int KEY `janitor` (`completed`,`heartbeat`,`worker`,`dirty`) -- datetime,datetime,varchar(255),tinyint
This works because workerpid is enough to tell us whether a job definition is in process (or was, and has not been cleaned yet.) and makes the following query run against a super small index…
SELECT `id`,GET_LOCK(CONCAT('foo_',`id`),0) as mylock FROM `foo_jobs` WHERE `priority` = '0' AND `workerpid` IS NULL AND IS_FREE_LOCK(CONCAT('foo_,`id`)) = 1 LIMIT 1
If you’re interested in what dark monstrosity could possibly require queries like these (and are a brave PHP developer) I invite you to check out the jobs system
Lets say you have the CouchDB classes (located here) all compiled together and included into your test.php script. Lets also say that you have created a database with the built-in web ui called “testing”. Finally let us say that your test.php has the following code in it, which would add a record to the db every time it is run. (i know that the data in the document serves no useful purpose… but really I just want to figure out this map/reduce thing so that I can make awesome views… so this suffices sufficiently.)
require_once dirname( dirname( __FILE__ ) ) . '/includes/couchdb.php'; $couchdb = new CouchDB('testing', 'localhost', 5984); $key = microtime(); $result = $couchdb->send( '/'.md5($key), 'put', json_encode( array( "_id" => md5($key), "time" => $key, 'md5' => md5($key), 'sha1' => sha1($key), 'crc' => crc32($key) ) ) ); print_r($result->getBody(true));
After running the code a bunch of times you would end up with a bunch of documents which look more or less like this:
(click for full size)Now lets say you want to write a view that told you what the first characters of the _id were and how many documents share that first letter. This is analogous to the following in MySQL
SELECT LEFT(md5, 1) AS `lchar`, count(md5) FROM `md5table` GROUP BY `lchar`
Your map function is easy, because you dont have any selection criteria, so we process all rows
function(doc){ emit(doc._id,doc); }
The reduce function is where the actual programming comes in… And it seems there aren’t many well explained examples of exactly how to do this (I just brute forced it by trial and error)
function(key, values, rereduce) { var output = {}; if ( rereduce ) { // key is null, and values are values returned by previous calls // // see http://wiki.apache.org/couchdb/Introduction_to_CouchDB_views // // essentially we are taking the previously reduced view, and the // reduced view for new records, and we are reducing those two things // together. Summarizing two summaries, essentially for ( var i in values ) { // here we have multiple prebuilt output objects and we're simply combining them // just like below we have an array with a numeric id and an output object // // retrieve a summary var vals = values[i]; for ( var key in vals ) { // debugging // log(key); // // store in or increment our new output object if ( output[key] == undefined ) output[key] = vals[key]; else output[key] = output[key] + vals[key]; } } } else { // key is an array, which we dont care about, and values are the // values returned by the map // // see http://wiki.apache.org/couchdb/Introduction_to_CouchDB_views // // we are taking each document and processing that, reducing it down // to a summary object (output) for each of the rows passed for ( var i in values ) { // we have an array, values, with numeric ids and a document objects // // retrieve a document var doc = values[i]; // get what we want from it, the first char of the md5 var key = doc._id.substr(0, 1); // debugging // log( key + " :: " + doc._id ); // // store or increment the output object if ( output[key] !== undefined ) output[key] = output[key] + 1; else output[key] = 1; } } // done return output; }
and in code, using a temporary view, ( if you used this view all the time you would want to make it permanent… but this is about how to lay out a reduce function, nothing more ) so request code that looks like this
$view = array( 'map' => 'function(doc){ emit(doc._id,doc); }', 'reduce' => ' function(key, values, rereduce) { var output = {}; if ( rereduce ) { // key is null, and values are values returned by previous calls for ( var i in values ) { var vals = values[i]; for ( var key in vals ) { // log(key); if ( output[key] == undefined ) output[key] = vals[key]; else output[key] = output[key] + vals[key]; } } } else { // key is an array, which we dont care about, and values are the values returneb by the map for ( var i in values ) { var doc = values[i]; var key = doc._id.substr(0, 1); // log( key + " :: " + doc._id ); if ( output[key] !== undefined ) output[key] = output[key] + 1; else output[key] = 1; } } return output; } ' ); $result = $couchdb->send('/_temp_view', 'POST', json_encode($view) ); print_r($result->getBody(true));
would give you output that looks like this:
stdClass Object ( [rows] => Array ( [0] => stdClass Object ( [key] => [value] => stdClass Object ( [0] => 15 [1] => 17 [2] => 16 [3] => 13 [4] => 27 [5] => 18 [6] => 26 [7] => 15 [8] => 18 [9] => 21 [a] => 12 [b] => 23 [c] => 20 [d] => 27 [e] => 28 [f] => 26 ) ) ) )
I hope this helps somebody out.
why? i dunno… just because… just a toy…
no sql, no flat file, no write permissions required anywhere, no fuss
class mc_chat { var $chan = null; var $mc = null; var $ret = 5; function __construct($memcached, $channel, $retention=5) { $this->mc = $memcached; $this->chan = $channel; $this->ret = $retention; } function messages( $from=0 ) { $max = (int)$this->mc->get("$this->chan:max:posted"); $min = (int)$this->mc->get("$this->chan:min:posted"); $messages = array(); for ( $i=$min; $i< =$max; $i++ ) { if ( $i < $from ) continue; $m = $this->get($i); if ( $m['user'] && $m['message'] ) $messages[$i] = $m; } return $messages; } function get($id) { return array( 'user' =>(string)$this->mc->get("$this->chan:msg:$id:user"), 'message' => (string)$this->mc->get("$this->chan:msg:$id"), ); } function add($user, $message) { $id = (int)$this->mc->increment("$this->chan:max:posted"); if ( !$id ) { $id=1; $this->mc->set("$this->chan:max:posted", 1); } $this->mc->set("$this->chan:msg:$id:user", (string)$user); $this->mc->set("$this->chan:msg:$id", (string)$message); if ( $id >= $this->ret ) { if ( !$this->mc->increment("$this->chan:min:posted") ) $this->mc->set("$this->chan:min:posted", 1); } } } $mc = new Memcache; $mc->connect('localhost', 11211); $keep_messages = 10; $chatter_id = 1; $chat = new mc_chat($mc, 'chat-room-id', $keep_messages); $chat->add($chatter_id, date("r").": $chatter_id : foo"); $chat->messages(37); // messages only above id=37 $chat->messages(); // all the latest messages
I’ve been working, gradually, on a project using an sqlite3 database (for its convenience) and found myself missing the clean elegance of wpdb… so I implemented it. It was actually really easy to do, and I figured I would throw it up here for anyone else wishing to use it. The functionality that I build this around is obtainable here: http://php-sqlite3.sourceforge.net/pmwiki/pmwiki.php (don’t freak… its in apt…)
With this I can focus on the sql, which is different enough, and not fumble over function names and such… $db = new sqlite_wpdb($dbfile, 3); var_dump($db->get_results(“SELECT * FROM `mytable` LIMIT 5″));
the code is below… and hopefully not too mangled…
< ?php class sqlite_wpdb { var $version = null; var $db = null; var $result = null; var $error = null; function sqwpdb($file, $version=3) { return $this->__construct($file, $version); } function __construct($file, $version=3) { $function = "sqlite{$version}_open"; if ( !function_exists($function) ) return false; if ( !file_exists($file) ) return false; if ( !$this->db = @$function($file) ) return false; $this->version = $version; $this->fquery = "sqlite{$this->version}_query"; $this->ferror = "sqlite{$this->version}_error"; $this->farray = "sqlite{$this->version}_fetch_array"; return $this; } function escape($string) { return str_replace("'", "''", $string); } function query($query) { if ( $this->result = call_user_func($this->fquery, $this->db, $query) ) return $this->result; $this->error = call_user_func($this->ferror, $this->db); return false; } function array_to_object($array) { if ( ! is_array($array) ) return $array; $object = new stdClass(); foreach ( $array as $idx => $val ) { $object->$idx = $val; } return $object; } function get_results($query) { if ( !$this->query($query) ) return false; $rval = array(); while ( $row = $this->array_to_object(call_user_func($this->farray, $this->result)) ) { $rval[] = $row; } return $rval; } function get_row($query) { if ( ! $results = $this->get_results($query) ) return false; return array_shift($results); } function get_var($query) { return $this->get_val($query); } function get_val($query) { if ( !$row = $this->get_row($query) ) return false; $row = get_object_vars($row); if ( !count($row) ) return false; return array_shift($row); } function get_col($query) { if ( !$results = $this->get_results($query) ) return false; $column = array(); foreach ( $results as $row ) { $row = get_object_vars($row); if ( !count($row) ) continue; $column[] = array_shift($row); } return $column; } } ?>
I’ve always wanted to write my own simple shell in php. Call me a glutin for punishment, but it seems like something that a lot of people could use to be able to do… If your web app had a command line interface for various things… like looking up stats, or users, or suspending naughty accounts, or whatever…. wouldnt that be cool and useful? Talk about geek porn. Anyways this this morning I got around to tinkering with the idea, and here is what i came up with… It’s rough, and empty, but its REALLY easy to extend and plug into any php application.
apokalyptik:~/phpshell$ ./shell.php /home/apokalyptik/phpshell > hello hi there /home/apokalyptik/phpshell > hello world hi there world /home/apokalyptik/phpshell > cd .. /home/apokalyptik/ > cd phpshell /home/apokalyptik/phpshell > ls shell.php /home/apokalyptik//phpshell > exit apokalyptik:~/phpshell$ ./shell.php
See the source here: shell.phps
We use dirname() a lot in php to make relative paths work from multiple locations like so. The advantages are many:
require dirname( dirname( __FILE__ ) ) . '/required-file.php'; $data = file_get_contents( dirname(__FILE__).'/data/info.dat');
But in bash we often dont do the same thing, we settle for the old standby “../”. Which is a shame because unless your directory structure is set up exactly right, and you have proper permissions, and you run the command from the right spot, it doesnt work as planned. I think part of the reason is that its not obvious how to reliably get a full path to the script from inside itself. Another reason is that ../ is shorter to type and easier to remember. Finally there’s always one time scripts for which this methodology is overkill. But if you’re planning to write a script which other people will (or might) be using, I think it’s good practice to do it right. Googling for things you’d think to search for on this subject does not yeild very informative results, or incomplete (incorrect) methods… so… here’s how to do the above php in bash:
source $(dirname $(dirname $(readlink -f $0)))/required-file.sh data=$(cat $(dirname $(readlink -f $0))/data/info.dat)
Hope this helps someone 
As a side note, the OSX readlink binary functions differently. You’ll want to use a package manager to install gnu coreutils, and iether use greadlink, or link greadlink to a higher precedence location on your $PATH (I have /opt/local/bin:/opt/local/sbin: at the beginning of my $PATH)