带有游标的存储过程以奇怪的方式执行

I have a stored procedure, which should process rows in a table using a cursor. The procedure works most of the time, but sometimes it just does not execute fully. I know this because I have a simple debugging facility, embedded into the code, which logs specific lines and variables into dedicated debug table. Most interesting that the problem does always occur when running from PHP. If I use mysql client I never got this problem.I have a stored procedure, which should process