What are some best practices for counting and manipulating characters in PHP strings efficiently?

When counting and manipulating characters in PHP strings, it is important to use built-in functions efficiently to achieve optimal performance. Some best practices include using functions like strlen() to count the length of a string, substr() to extract parts of a string, and str_replace() to replace characters in a string. Additionally, using regular expressions with functions like preg_match() can be helpful for more complex manipulations.

// Counting characters in a string
$string = "Hello, World!";
$length = strlen($string);
echo "Length of string: " . $length;

// Extracting part of a string
$substring = substr($string, 0, 5);
echo "Substring: " . $substring;

// Replacing characters in a string
$newString = str_replace("Hello", "Hi", $string);
echo "Replaced string: " . $newString;

// Using regular expressions
if (preg_match("/[0-9]+/", $string, $matches)) {
    echo "Numbers found in string: " . $matches[0];
}