Using PHP's substr() Function for String Manipulation

In PHP, string handling is a common task, and the substr() function provides a convenient way to extract a part of a string.

The function signature is:

string substr ( string $string , int $start [, int $length ] )

Parameters:

$string : the input string to be sliced.

$start : the zero‑based position where extraction begins.

$length (optional): the number of characters to extract; if omitted, extraction continues to the end of the string.

Examples:

Example 1: Extract a substring with specified length

$str = "Hello, World!";
$sub_str = substr($str, 0, 5);
echo $sub_str; // outputs "Hello"

This extracts the first five characters of the string.

Example 2: Extract without specifying length

$str = "Hello, World!";
$sub_str = substr($str, 7);
echo $sub_str; // outputs "World!"

Here the extraction starts at position 7 and continues to the end.

Example 3: Using a negative start offset

$str = "Hello, World!";
$sub_str = substr($str, -6, 5);
echo $sub_str; // outputs "World"

A negative start counts from the end of the string; this example extracts five characters starting six positions from the end.

The substr() function is flexible, but note that if $start exceeds the string length, an empty string is returned, and a negative $length is treated as zero.

By mastering substr() , developers can efficiently manipulate strings in PHP applications.