Rick Baker's Personal Website

There are times when you want to run a PHP script in the background, something that is triggered by a user, but you don’t want them to have to wait for it to complete.   A couple ways to accomplish this, but I’ll focus on one in particular.  That’s making an asynchronous call using AJAX.

It’s pretty simple actually.  The first thing is in your script that you want to run in the background, you need to make sure it runs long enough to complete, and that also it won’t die when  the connection is aborted.  So, at the top of this PHP script, you’ll want to add these 2 lines:

 ignore_user_abort(1);
 set_time_limit(0);
 

Now for how to actually get that script running in the background.  We’ll be using javascript and taking advantage of the YUI library since it makes it particularly easy.

Basically, what happens is an async call is made to the script, and then the connection is aborted, so the script continues to run and the user can go on doing whatever they want.  The key is you don’t want to abort the connection to fast.  If it’s aborted right after it’s made the script won’t even have time to start.  So, we need to give it a couple seconds before actually aborting.   Here’s the javascript for this:

 <script src="http://yui.yahooapis.com/2.8.0r4/build/yahoo/yahoo-min.js"></script>
 <script src="http://yui.yahooapis.com/2.8.0r4/build/event/event-min.js"></script>
 <script src="http://yui.yahooapis.com/2.8.0r4/build/connection/connection_core-min.js"></script>
<script type="text/javascript">
var spawnCallback = {
success: function(o) {
},
failure: function(o) {
},
timeout: 2000
};

function spawnProcess() {
YAHOO.util.Connect.asyncRequest('GET','url/to/script.php',spawnCallback);
}
</script>

And that’s about it.  Then you just need to call the spawnProcess() function and it will trigger your designated PHP script which will run in the background until finished.

Over time some of your MySQL tables may end up fragmented.  If you run any type of diagnostic script like mysqltuner, it will even tell you how many of your tables are fragmented.  You can easily fix this by optimizing the fragmented tables.  The problem is, you might not know which tables are fragmented.

Here’s a quick little query you can run that will give you the tables that are fragmented and how badly fragmented they are:

select TABLE_NAME,Data_free
from information_schema.TABLES
where TABLE_SCHEMA NOT IN ('information_schema','mysql')
and Data_free > 0;

Just in case anyone didn’t catch the optimize bit above. Once you’ve found your fragmentend tables, you can fix them with the following query, replacing %TABLENAME% with the actual table name:

optimize table %TABLENAME%

Ever have a several gig MySQL dump and only need to extract a table or two out of it?  Here’s something you can run from the command line that will split all of the tables into individual files.  You’ll need to know if your dump file has the CREATE TABLE format included or is just the data.  If it’s just the data then you can change where it says CREATE TABLE to LOCK TABLES below.

One thing to note.  If awk ends up giving you an error such as “Program Limit Exceeded”, then you can use gawk instead and it should work without issues.

cat dumpfile.sql | awk 'BEGIN {
output = "comments"; } $data ~ /^CREATE TABLE/ {
 close(output);
 output = substr($3,2,length($3)-2); }
{ print $data >> output }'