Allowed memory size of 104857600 bytes exhausted (tried to allocate 45 bytes) in str_replace()

In my project I'm using xmlrpc communication to get the data from the client

But today while communicating I got this error..

There is no increase in request , request rate is normal.. and memory is also not full..

Then why I'm getting this error?

It occurred due to invalid xml data?

Can we produce infinite loop in xml data? because of this I got this error?