To Log your error in syslog using php use this :
/*
** Logging Data showing error
*/
openlog("myScriptLog", LOG_NDELAY, LOG_LOCAL6);
your code here
syslog(LOG_DEBUG, "Non Availability of Participant ID");
closelog();
Before this make a entry in syslog.conf :
local6.* /var/log/php.log
* represents that all types of logs get entered in /var/log/php.log
Restart the syslog using : service syslog restart
now run your code.
Remember if you use LOG_PERROR then logs will get displayed also in console/code.