Introduction to the usage of PHP's count_chars() function

In PHP programming, string operations are very common. Sometimes we need to count the number of occurrences of each character in a string. In this case, we can use PHP's count_chars() function. This article will introduce in detail how to use PHP's count_chars() function.

1. Overview of count_chars() function

The count_chars() function is a built-in function in PHP, used to count the number of occurrences of each character in a string.

bool count_chars ( string $string [, int $mode = 0 ] )

Parameter description:

$string: A string in which the number of occurrences of characters needs to be counted.

$mode: Optional parameter, specify the return form:

• 0 (or default value): Returns a one-dimensional array, counting the occurrences of all ASCII codes.
• 1: Returns a list of characters.
• 2: Returns a list of all occurrences of non-repeating characters.

2. Use the count_chars() function to count the number of times a character appears

1. Count the number of times each character appears

The following is a simple example of.

$str = "Hello World!";
$char_count = count_chars($str, 1);

print_r($char_count);
?>

The output result is as follows:

Array
(

[32] => 1
[33] => 1
[72] => 1
[101] => 1
[108] => 3
[111] => 2
[114] => 1
[119] => 1
[100] => 1

)

As you can see from the result, the count_chars() function returns An array is created, the keys of the array are ASCII code values, and the values ​​are the number of times a character appears. For example, the ASCII code value of the character "H" is 72, and it appears once in the string.

2. Count the character list where non-repeating characters appear

The following example demonstrates how to return a list of all non-repeating characters in a string.

$str = "Hello World!";
$char_list = count_chars($str, 2);

foreach(str_split($char_list) as $char) {

echo $char . PHP_EOL;

}
?>

The output result is as follows:

H
e
l
o
W
r
d
!

As you can see from the results, the count_chars() function returns a string containing all non-repeating characters in the string. Moreover, we used the str_split() function to convert the string into a character array and output it one by one in the foreach loop.

3. Summary

This article introduces in detail the usage of the count_chars() function in PHP, including counting the number of occurrences of each character and returning a list of non-repeating characters. We can use this function to quickly count the characters in the string, which brings great convenience to our programming.

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