Description:
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The documentation for flock() only hints that the default behaviour is blocking in the description of the operation parameter. Based on the conversation I just had in ##php, this may be confusing to people. :)

For clarity, may I suggest changing the third line of the description from:

PHP supports a portable way of locking complete files in an advisory way (which means all accessing programs have to use the same way of locking or it will not work). 

To something like:

PHP supports a portable way of locking complete files in an advisory way (which means all accessing programs have to use the same way of locking or it will not work). By default, this function will block until the requested lock is acquired; this may be controlled (on non-Windows platforms) with the LOCK_NB option documented below.