Some (php?) command is flooding error_log

[Richard G]

I had this before and it's very disturbing. It doesn't break anything, but it's very annoying that I can't find it.

This is sometimes occuring a lot of times in my /var/log/http/error_log withtout any time stamp, tonight it even flooded my log according to a mail from my system:

Time: Mon May 19 23:29:41 2014 +0200
Alert: *Error* Log line flooding/looping in /var/log/httpd/error_log. Reopening log file

And this is what the error_log is being flooded with:

Usage: host [-aCdlriTwv] [-c class] [-N ndots] [-t type] [-W time]
[-R number] [-m flag] hostname [server]
-a is equivalent to -v -t ANY
-c specifies query class for non-IN data
-C compares SOA records on authoritative nameservers
-d is equivalent to -v
-l lists all hosts in a domain, using AXFR
-i IP6.INT reverse lookups
-N changes the number of dots allowed before root lookup is done
-r disables recursive processing
-R specifies number of retries for UDP packets
-s a SERVFAIL response should stop query
-t specifies the query type
-T enables TCP/IP mode
-v enables verbose output
-w specifies to wait forever for a reply
-W specifies how long to wait for a reply
-4 use IPv4 query transport only
-6 use IPv6 query transport only
-m set memory debugging flag (trace|record|usage)

So it seems apache or some php script is wrongly using the host command, which causes the host command to respond with "the usage of host is like this" in the error_log.

How can I find what is causing this? I tried grep but the name "host" or "host " appears in so many files and so many files (thing of database files, lots of scripts etc.) that it's undoable to check them all manually.
Anybody a clue on how to find the source of the problem?

Or is it possible to (temporarily) expand the apache log that more information will be available about where it's coming from (apache or php script)?