In PHP, strpos() is a built-in function used to find the position of the first occurrence of a substring inside another string.

🔹 Syntax:

strpos(string $haystack, mixed $needle, int $offset = 0): int|false

• $haystack: The main string you want to search in.
• $needle: The substring you're looking for.
• $offset (optional): Start searching from this position.
• Returns:
  • The position (0-based index) of the first occurrence of $needle.
  • false if $needle is not found.

✅ Basic Example:

<?php
$text = "Hello, world!";
$pos = strpos($text, "world");

if ($pos !== false) {
    echo "Found at position: $pos";  // Output: Found at position: 7
} else {
    echo "Not found";
}
?>

Notice: === is used instead of == to strictly check for false (since position 0 is valid).

🔍 Example with Offset:

<?php
$text = "I love PHP. PHP is great!";
$pos = strpos($text, "PHP", 10);

echo $pos;  // Output: 15 (the second occurrence)
?>

❌ Not Found Example:

<?php
$text = "Learning Laravel!";
$pos = strpos($text, "PHP");

if ($pos === false) {
    echo "Not found";  // Output: Not found
}
?>

⚠️ Common Mistake:

$pos = strpos("PHP is cool", "PHP");
if ($pos) {
    echo "Found";   // ❌ Won't echo because 0 == false
}
// Always use !== false to avoid this trap!

🎯 Use Case: Check if a string contains another string

function contains($text, $keyword) {
    return strpos($text, $keyword) !== false;
}

echo contains("Laravel is awesome", "awesome") ? "Yes" : "No";  // Output: Yes