Why is the transaction log filling up? _PHP Tutorial

The SQL Server transaction log may fill up, preventing subsequent database operations, including UPDATE, DELETE, INSERT, and CHECKPOINT.
Transaction log filling will cause 1105 error:
Can't allocate space for object syslogs in database dbname because
the logsegment is full.
If you ran out of space in syslogs, dump
the transaction log.
Otherwise use ALTER DATABASE or
sp_extendsegment to increase the size of the segment.
This phenomenon may occur in any database, including Master and TempDB. Some unforeseen factors may consume log space.
For example:
A large transaction, especially batch data updates, insertions or deletions.
An uncommitted transaction.
The checkpoint handler requires too much bandwidth for truncation.
Exceeding the threshold when truncation
The result of the interaction of the above conditions.
The marked transaction for publishing was not read by the log reader