Detailed explanation of PHP file lock concurrency operation

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(&#39;/tmp/lock.txt&#39;, &#39;r+&#39;);

/* Activate the LOCK_NB option on an LOCK_EX operation */if(!flock($fp, LOCK_EX | LOCK_NB)) {
    echo &#39;Unable to obtain lock&#39;;
    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(&#39;/tmp/lock.txt&#39;, &#39;r+&#39;);

/* Activate the LOCK_NB option on an LOCK_EX operation */if(!flock($fp, LOCK_EX | LOCK_NB)) {
    echo &#39;Unable to obtain lock&#39;;
    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).

Related recommendations:

How PHP uses file locks to solve high concurrency problems

php uses file locks to solve high concurrency problems

How to solve high concurrency in php

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