Mastering PHP substr(): How to Extract Substrings Effectively

Function Overview

The substr() function returns a portion of a string, defined by a start position and an optional length.

Signature

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

Parameters $string (string): The input string. $start (int): If non‑negative, the extraction starts at that position counted from 0; if negative, counting starts from the end of the string. $length (int, optional): Determines how many characters to include. Positive values limit the result to that many characters from $start. Negative values omit that many characters from the end. Zero, FALSE or NULL produce an empty string. If omitted, the substring runs to the end of $string.

Return Value

On success, the extracted substring is returned. If the start position exceeds the string length or an error occurs, FALSE is returned.

Examples

<?php
echo "1) " . var_export(substr("pear", 0, 2), true) . PHP_EOL;
echo "2) " . var_export(substr(54321, 0, 2), true) . PHP_EOL;
echo "3) " . var_export(substr(new apple(), 0, 2), true) . PHP_EOL;
echo "4) " . var_export(substr(true, 0, 1), true) . PHP_EOL;
echo "5) " . var_export(substr(false, 0, 1), true) . PHP_EOL;
echo "6) " . var_export(substr("", 0, 1), true) . PHP_EOL;
echo "7) " . var_export(substr(1.2e3, 0, 4), true) . PHP_EOL;
?>

Output:

1) 'pe'
2) '54'
3) 'gr'
4) '1'
5) false
6) false
7) '1200'