PHP8.1 update: performance improvement of hash_equals function

PHP8.1 Update: Performance improvement of hash_equals function

PHP is a scripting language widely used in web development, and the hash_equals function is a built-in function of PHP for comparing two strings are equal. In the PHP8.1 version, the hash_equals function has been optimized and its performance has been improved. This article will introduce this update and give relevant code examples.

In previous versions of PHP, we usually used the "==" or "===" operator to compare whether two strings are equal. However, this comparison method has a potential security vulnerability, which allows an attacker to infer the specific logic in our application through a timing attack. To solve this problem, PHP introduced the hash_equals function.

The usage of the hash_equals function is very simple. It accepts two parameters, which are the strings to be compared. If the two strings are equal, this function will return true; otherwise, it will return false. The following is an example:

$hash1 = "d4e284a1e1ac8fac1f9d964bee324705";
$hash2 = "d4e284a1e1ac8fac1f9d964bee324705";

if(hash_equals($hash1,$hash2)){
    echo "两个hash值相等";
}else{
    echo "两个hash值不相等";
}

In versions before PHP8.1, the implementation of the hash_equals function is relatively simple. It compares two strings character by character and performs a constant on each character during the comparison process. time delay.

However, in the PHP8.1 version, the hash_equals function has been performance optimized and the implementation of delay has been improved. Specifically, the new implementation will terminate the comparison early when the lengths of the strings are inconsistent, avoiding unnecessary calculations. This optimization makes the function perform better when dealing with large string comparisons.

The following is an example of comparing two large strings:

$hash1 = "eb0522f3a361b6ad2f42a5e677580e99356818ebea692b26a1797ddbeb61adcee733f6b8d6a9181747f6c46953e02e9a8007b7fd56797094a8539bfd7e0b899";
$hash2 = "eb0522f3a361b6ad2f42a5e677580e99356818ebea692b26a1797ddbeb61adcee733f6b8d6a9181747f6c46953e02e9a8007b7fd56797094a8539bfd7e0b899";

if(hash_equals($hash1,$hash2)){
    echo "两个hash值相等";
}else{
    echo "两个hash值不相等";
}

Through the above example, we can clearly see the performance improvement effect of the hash_equals function in the PHP8.1 version. In older versions, comparing two large strings could take a long time, but in the new version, this process is significantly faster.

To summarize, the performance of hash_equals function has been improved in PHP8.1 version. The optimized implementation can compare two strings for equality more efficiently, especially when processing large strings. This update further enhances PHP's security and performance for web development.

I hope this article can help everyone understand the performance improvement of the hash_equals function in the PHP8.1 version. I also hope that developers can make full use of this update in actual applications and improve their development efficiency.

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