Count the number of occurrences of a substring using the PHP substr_count() function

In PHP development, counting the number of times a certain substring appears in a string is a very common requirement. For example, we may need to count the number of times a certain keyword appears in an article, or count the number of times a certain symbol appears in user input. At this time, we can use PHP's built-in substr_count() function to achieve this.

The substr_count() function is used to count the number of times another substring appears in a string. The basic syntax is as follows:

int substr_count ( string $haystack , string $needle [, int $offset = 0 [, int $length ]] )

Among them, $haystack is the string to be searched, $needle is the substring to be searched, $offset is the offset, and $length is the length to be searched. If you need to count the number of occurrences of a substring in the entire string, you can omit the $offset and $length parameters.

The following is an example to illustrate how to use the substr_count() function to calculate the number of occurrences of a substring:

<?php
    $str = "Hello World! Hello PHP!";
    $count = substr_count($str, "Hello");
    echo "The string 'Hello' appears $count times in the string '$str'";
?>

Run the above code, the output result is as follows:

The string 'Hello' appears 2 times in the string 'Hello World! Hello PHP!'

In In this example, we first define a string $str, and then use the substr_count() function to count the number of times the substring "Hello" appears in the string. Finally, use the echo statement to output the results.

In addition to counting the number of occurrences of a substring in the entire string, we can also count the number of times a substring appears in a certain paragraph of the string by specifying $offset and $length. For example:

<?php
    $str = "This is a long string.";
    $count = substr_count($str, "is", 3, 10);
    echo "The string 'is' appears $count times in the string '$str'";
?>

Run the above code, the output result is as follows:

The string 'is' appears 1 times in the string 'This is a long string.'

In this example, we use the substr_count() function to calculate the 10-character length starting from the fourth character. The number of occurrences of "is" in the substring.

It should be noted that the substr_count() function counts the number of non-overlapping substrings. For example, in the string "abababa", the number of occurrences of the substring "aba" is 2, not 3.

To sum up, the substr_count() function is a very useful function in PHP to count the number of occurrences of a substring in a string. This function can be used whether doing page analysis or character processing.

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