PHP Cookbook: Accessing Substrings

Problem
You want to know if a string contains a particular substring. For example, you want to find out if an email address contains a @.

Solution
Use strpos()

<?php
if (strpos($_POST['email'], '@') === false) {
print 'There was no @ in the e-mail address!';
}
?>

Discussion
The return value from strpos( ) is the first position in the string (the “haystack”) at which the substring (the “needle”) was found. If the needle wasn’t found at all in the haystack, strpos( ) returns false. If the needle is at the beginning of the haystack, strpos( ) returns 0, since position 0 represents the beginning of the string. To differentiate between return values of 0 and false, you must use the identity operator (===) or the not–identity operator (!==) instead of regular equals (==) or not-equals (!=). Example 1-8 compares the return value from strpos( ) to false using ===. This test only succeeds if strpos returns false, not if it returns 0 or any other number.

See Also
Documentation on strpos( ) at http://www.php.net/strpos

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