How can PHP developers optimize their code for efficient string manipulation, especially when dealing with varying word lengths?

When dealing with varying word lengths in string manipulation, PHP developers can optimize their code by using functions like `strlen()` to get the length of a string and `substr()` to extract substrings efficiently. By dynamically calculating the length of words and using appropriate string manipulation functions, developers can ensure their code is efficient and scalable.

// Example code snippet for optimizing string manipulation with varying word lengths
$string = "Hello, world!";
$words = explode(" ", $string);

foreach ($words as $word) {
    $length = strlen($word);
    $substring = substr($word, 0, $length / 2);
    
    // Perform operations on $substring
    echo $substring . " ";
}