PHP strpos Examples

Important: use the correct comparsion operator!With strpos() functions always use the identical operator "===" or "!==" and compare to "false"

CORRECT

if (strpos($str, $substr) === false) {

if (strpos($str, $substr) !== false) {

WRONG

if (strpos($str, $substr) != false) {

if (strpos($str, $substr) == false) {

The reason for using the identical operators (that also check for the type of the value) "===" or "!==" is that strpos() might return "0" for match at the beginning or "false" for no match which cannot be distinguished by "==" or "!=".

Case Sensitivity

Simply use stripos() instead of strpos()

strpos()	case sensitive searching
stripos()	case insensitive searching

Search From Offset

If you want to continue a search or want to skip something at the start use an offset as third parameter:

if (strpos($str, $substr, 5) === false) {

By using the return value of strpos() you can do repeated searches:

$pos1 = strpos($str, $substr);
$pos2 = strpos($str, $substr, $pos1 + strlen($pos1));

Search Backwards

There is an additional set of methods for backwards searching:

strrpos()	case sensitive backwards searching
strripos()	case insensitive backwards searching

Extract Found Strings

If you want to extract a string at the position you've found you need to use the substr() method. An example:

$pos = strpos($str, $substr);
$result = substr($str, $pos);

When not to use strpos()?

Do not use strpos() if you want to do the following things:

Test for a pattern at the start or end of a string -> use preg_match()
Extract multiple substrings -> use preg_match()
Match a string for a complex pattern -> use preg_match()
If you want to split a string a delimiters -> use strpbrk()

About Performance

If you are wondering how fast strpos() is compared to using regular expressions check this post: strpos() vs preg_match()

PHP strpos Examples Edit Cheat Sheet