The `strpos()` function in PHP is used to find the position of the first occurrence of a substring in a string. It's case-sensitive and returns the position as an integer, or `false` if the substring is not found.PHP 8.PHP 8.1,PHP 8.2,PHP 8.3,and PHP 8.4.

Basic Syntax

<?php
strpos(string $haystack, string $needle, int $offset = 0): int|false
?>

Example in PHP 8.2

<?php
$text = "Hello, welcome to PHP 8.2 programming!";
$search = "PHP";
// Find the position of "PHP" in the string
$position = strpos($text, $search);
if ($position !== false) {
echo "The substring '$search' was found at position: $position";
} else echo "The substring '$search' was not found in the text.";
}
// Output: The substring 'PHP' was found at position: 18
?>

Important Notes for PHP 8.2

1. Strict Comrison**: Always use `!== false` for checking if a substring was found, because `0` is a valid position but evaluates to `false` in loose comparison.
2. Case Sensitivity**: For case-insensitive search, use `stripos()` instead.
3. Multibyte Strings**: For multibyte character strings (like UTF-8)e `mb_strpos()`.
5. Needle as Integer**: In PHP 8.2, passing an integer as needle is deprecated (previously it was treated as ASCII value).

Edge Case Example

<?php
// Searching for a substring at position 0
$result = strpos("PHP is great", "PHP");
if ($result !== false) {
echo "Found at position $result"; // Output: Found at position 0
} else {
echo "Not found";
}
// This would fail with loose comparison:
if ($result == false) {
echo "This would incorrectly execute for position 0";
}
?>

Remember that string positions start at 0, not 1, in PHP.