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This article mainly shares with you the detailed explanation of PHP file lock concurrent operation. The default: PHP's file operation function is not in a blocking state, but in a free operation state. I hope it can help everyone.
Conditions:
When a script operation is required and another script operation needs to be blocked, a file lock is required.
Lock operation process:
Add the lock first, check whether the lock is added successfully, and use it again if it is successful!
Lock type:
Read lock: s-Lock (share-lock) shared lock, the expected additional lock before the read operation. As a result, concurrent reads are allowed and additional write operations are blocked.
Write lock: x-lock (exclusive-lock) exclusive lock, exclusive lock, try to add the lock type before writing operation. As a result, other scripts cannot read or write.
Intention lock: All scripts that operate resources follow a convention to use file locks (convention).
Blocking: refers to that after the previous operation is unlocked, the next operation to lock the file can continue to be executed.
Function:
bool flock ( resource $handle , int $operation [, int &$wouldblock ] )
Type parameters ($operation
): LOCK_SH
read lock and LOCK_EX
write lock
Example:
Use Read lock:
Use write lock:
You can use LOCK_NB 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($fp);
Unlock: in Before PHP 5.3.2, the lock would also be released by fclose() (which will be automatically called after the script ends). Now it can only be unlocked manually through flock($fp,LOCK_UN)
Default: PHP's file operation function is not in a blocking state, but in a free operation state.
Conditions:
When a script operation is required and another script operation needs to be blocked, a file lock is required.
Lock operation process:
Add the lock first, check whether the lock is added successfully, and use it again if it is successful!
Lock type:
Read lock: s-Lock (share-lock) shared lock, the expected additional lock before the read operation. As a result, concurrent reads are allowed and additional write operations are blocked.
Write lock: x-lock (exclusive-lock) exclusive lock, exclusive lock, try to add the lock type before writing operation. As a result, other scripts cannot read or write.
Intention lock: All scripts that operate resources follow a convention to use file locks (convention).
Blocking: refers to that after the previous operation is unlocked, the next operation to lock the file can continue to be executed.
Function:
bool flock ( resource $handle , int $operation [, int &$wouldblock ] )
Type parameters ($operation
): LOCK_SH
read lock and LOCK_EX
write lock
Example:
Use Read lock:
Use write lock:
You can use LOCK_NB 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($fp);
Unlock: in Before PHP 5.3.2, the lock would also be released by fclose() (which would be automatically called after the script ends). Now it can only be unlocked manually through flock($fp,LOCK_UN)
.
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