Using PHP strpos() to Find Character and Substring Positions

In PHP, string handling often requires locating the position of a specific character or substring, which can be done using the built‑in strpos() function.

1. Basic usage of strpos()

The function returns the position of the first occurrence of a needle in a haystack, or false if not found. Its signature is:

int strpos ( string $haystack , mixed $needle [, int $offset = 0 ] )

$haystack is the target string, $needle is the character or substring to search for, and $offset (optional) specifies where to start the search.

2. Example: finding a character

Given $str = "Hello, world!" , the following code finds the position of the character 'o' :

$pos = strpos($str, 'o');
if ($pos === false) {
    echo "Character 'o' not found";
} else {
    echo "Character 'o' is at position: " . $pos;
}

The script outputs: Character 'o' is at position: 4 .

3. Example: finding a substring

To locate the substring 'wor' :

$str = "Hello, world!";
$sub_str = 'wor';
$pos = strpos($str, $sub_str);
if ($pos === false) {
    echo "Substring 'wor' not found";
} else {
    echo "Substring 'wor' is at position: " . $pos;
}

The result is: Substring 'wor' is at position: 7 .

4. Example: using an offset

Searching for 'o' starting from index 5:

$str = "Hello, world!";
$sub_str = 'o';
$pos = strpos($str, $sub_str, 5);
if ($pos === false) {
    echo "Character 'o' not found";
} else {
    echo "Character 'o' is at position: " . $pos;
}

The output is: Character 'o' is at position: 8 .

Conclusion

The article demonstrates the basic syntax of strpos() and shows how to use it to locate characters, substrings, and to start searches from a specific offset, helping developers handle string‑related tasks more efficiently.

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