PHP substr() Function – Description, Parameters, Return Value, and Usage Examples

Function: substr() returns a portion of a string based on the supplied start position and optional length.

Parameters: string $string – the input string (must contain at least one character). int $start – if non‑negative, the extraction begins at this zero‑based index; if negative, counting starts from the end of the string. If the absolute value exceeds the string length, FALSE is returned. int $length (optional) – when positive, limits the number of characters returned; when negative, characters are omitted from the end of the string; when zero, FALSE, NULL, or 0, an empty string is returned. If omitted, extraction continues to the end of the string.

Return value: the extracted substring, or FALSE on failure.

Examples:

Example 1 – negative start values:

<?php
$rest = substr("abcdef", -1); // returns "f"
$rest = substr("abcdef", -2); // returns "ef"
$rest = substr("abcdef", -3, 1); // returns "d"
?>

Example 2 – mixed start and length values:

<?php
$rest = substr("abcdef", 0, -1); // returns "abcde"
$rest = substr("abcdef", 2, -1); // returns "cde"
$rest = substr("abcdef", 4, -4); // returns "" (empty string)
?>

Example 3 – using the function in echo statements:

<?php
echo substr('abcdef', 1); // outputs "bcdef"
echo substr('abcdef', 1, 3); // outputs "bcd"
echo substr('abcdef', 0, 4); // outputs "abcd"
echo substr('abcdef', -1, 1); // outputs "f"
?>

Additional note: individual characters can be accessed directly using array‑style indexing, e.g., $string = 'abcdef'; echo $string[0]; // a or echo $string[strlen($string)-1]; // f.