(PECL gearman >= 0.5.0)
GearmanWorker::addFunction — Register and add callback function
$function_name
   , callable $function
   [, mixed &$context
   [, int $timeout
  ]] )Registers a function name with the job server and specifies a callback corresponding to that function. Optionally specify extra application context data to be used when the callback is called and a timeout.
function_name
     The name of a function to register with the job server
function
     A callback that gets called when a job for the registered function name is submitted
context
     A reference to arbitrary application context data that can be modified by the worker function
timeout
     An interval of time in seconds
   成功时返回 TRUE, 或者在失败时返回 FALSE.
  
Example #1 Simple worker making use of extra application context data
<?php
# get a gearman worker
$worker= new GearmanWorker(); 
# add the default server (localhost)
$worker->addServer(); 
# define a variable to hold application data
$count= 0; 
# add the "reverse" function
$worker->addFunction("reverse", "reverse_cb", &$count);
# start the worker
while ($worker->work());
function reverse_cb($job, $count) 
{ 
  $count++; 
  return "$count: " . strrev($job->workload()); 
} 
?>
Running a client that submits two jobs for the reverse function would have output similar to the following:
1: olleh 2: dlrow