New functions in PHP8: efficient string search techniques for str_contains()

PHP8 is undoubtedly an important version of PHP at present. In addition to bringing better performance and security, it also introduces some very useful new features. One of the new features is the str_contains() function, which is used to find a specified substring in a string.

In the past, we usually used the strpos() function to find whether a certain substring exists in a string. For example, to find whether the "hello" substring is contained in the following string:

$string = "Hello, world!";
if (strpos($string, "hello") !== false) {
    echo "Found 'hello' in the string!";
} else {
    echo "Did not find 'hello' in the string!";
}

The result will be "Did not find 'hello' in the string!". This is because the strpos() function is case-sensitive.

The str_contains() function is not case-sensitive. It directly returns a Boolean value indicating whether the string contains the specified substring. Therefore, the above code can be rewritten using the str_contains() function:

$string = "Hello, world!";
if (str_contains($string, "hello")) {
    echo "Found 'hello' in the string!";
} else {
    echo "Did not find 'hello' in the string!";
}

The result will be "Found 'hello' in the string!". Because the str_contains() function will find whether the string contains the "hello" substring, it is not case-sensitive.

Using str_contains() instead of strpos() is not only more intuitive, but also more efficient. Because str_contains() will use some optimization techniques to improve the efficiency of string search. These optimization techniques include:

Optimization 1: Use the Boyer-Moore algorithm

The Boyer-Moore algorithm is an efficient string search algorithm, which is one of the underlying implementations of the str_contains() function. . The main idea of ​​the Boyer-Moore algorithm is to skip as many invalid characters as possible to reduce the number of searches.

For example, when finding the position of the string "hello" in "hello, world!", the Boyer-Moore algorithm will first start matching from the last character "o" of the string. If there is no match, the jump distance is calculated based on the number of occurrences of the character. In this example, the character "o" appears twice in the string "hello", so the Boyer-Moore algorithm will skip the search position forward by two characters to avoid repeated matches.

Using the Boyer-Moore algorithm can greatly improve the efficiency of string search, especially for those longer strings and longer substrings.

Optimization 2: Avoid copying strings multiple times

When using the strpos() function to search for a string, you usually need to copy the string and substring for comparison. This can cause increased memory usage, especially when the strings being operated on are long.

The str_contains() function avoids copying the string multiple times by using the reference counting mechanism. The reference counting mechanism is a memory management technology that can share the same copy of a string when multiple variables refer to the same string to avoid multiple copies.

Using the reference counting mechanism can avoid copying strings multiple times, thereby reducing memory usage and improving program performance.

Optimization 3: Implemented using C code

The str_contains() function is implemented using C code, so it is faster and more efficient than the strpos() function. When searching for a large number of strings, using the str_contains() function can greatly improve the execution speed of the program.

Summary

The str_contains() function is a very useful new feature in PHP8, which can be used to find specified substrings in strings. It not only makes our code more intuitive and easier to understand, but also improves the performance of the program through the use of optimization techniques.

If you need to perform string searches in PHP, consider using the str_contains() function for better performance and more efficient code.

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