PHP file lock concurrency operation detailed

This article is mainly to share with you the PHP file lock concurrency operation, the default: PHP file operation function, not blocking state, but free operation State, hope to help everyone.

Conditions:

• A file lock is required when a script operation is required to block additional script operations.

Lock Operation Flow:

• Lock first, detect if the lock is successful, if you use it successfully!

Lock type:

• Read Lock: S-lock (share-lock) shared lock, expected to increase lock before read operation. Causes, allows concurrent reads, and blocks additional writes.

• Write Lock: X-lock (Exclusive-lock) exclusive lock, exclusive lock, write operation before attempting to add a lock type. Cause, other scripts cannot be read or written.

• Intent Lock: All scripts that manipulate resources follow a convention to use file locks (conventions).

Blocking: Refers to the next action on a file lock to continue after the previous operation has been unlocked

Function:

BOOL Flock (resource $handle, int $operation [, int & $wouldblock])

Type parameter ( $operation ): LOCK_SH read lock and LOCK_EX write lock

Cases:
Use read lock:

Using Write Locks:

The LOCK_NB can be used to not block when the lock fails:

<?PHP$FP = fopen ('/tmp/lock.txt ', ' r+ ');/* Activate the LOCK_NB option on an LOCK_EX operation */if (!flock ($fp, LOCK_EX | LOCK_NB) {    echo ' unable to obtain lock ';    Exit (-1);} /* */fclose ($FP);

Unlock: Locks are also released by Fclose (automatically called after the script ends) before PHP 5.3.2, and can now be unlocked flock($fp,LOCK_UN) manually

Default: PHP file operation function, not blocking state, but free operation state.

Conditions:

• A file lock is required when a script operation is required to block additional script operations.

Lock Operation Flow:

• Lock first, detect if the lock is successful, if you use it successfully!

Lock type:

• Read Lock: S-lock (share-lock) shared lock, expected to increase lock before read operation. Causes, allows concurrent reads, and blocks additional writes.

• Write Lock: X-lock (Exclusive-lock) exclusive lock, exclusive lock, write operation before attempting to add a lock type. Cause, other scripts cannot be read or written.

• Intent Lock: All scripts that manipulate resources follow a convention to use file locks (conventions).

Blocking: Refers to the next action on a file lock to continue after the previous operation has been unlocked

Function:

BOOL Flock (resource $handle, int $operation [, int & $wouldblock])

Type parameter ( $operation ): LOCK_SH read lock and LOCK_EX write lock

Cases:
Use read lock:

Using Write Locks:

The LOCK_NB can be used to not block when the lock fails:

<?PHP$FP = fopen ('/tmp/lock.txt ', ' r+ ');/* Activate the LOCK_NB option on an LOCK_EX operation */if (!flock ($fp, LOCK_EX | LOCK_NB) {    echo ' unable to obtain lock ';    Exit (-1);} /* */fclose ($FP);

Unlocked: Before PHP 5.3.2, locks are also released by Fclose (automatically called after the end of the script) and can now be unlocked manually via the flock ($fp, Lock_un) .