In PHP, what is the significance of starting the counting at 0 when using functions like substr()?

When using functions like substr() in PHP, it's important to remember that the counting of characters starts at 0. This means that the first character in a string is at position 0, the second character is at position 1, and so on. If you want to extract a substring starting at a specific position, you need to adjust the starting index accordingly by subtracting 1.

$string = "Hello, World!";
$start = 5; // Start position (1-based index)
$length = 5; // Length of the substring
$adjusted_start = $start - 1; // Adjusted start position (0-based index)

$substring = substr($string, $adjusted_start, $length);
echo $substring; // Outputs "o, Wo"