Why preg_match() always validates as true when partial match?

Question

Recently been explerimenting with regular expressions and when I\'ve tried to confirm that the preg_match() function was not returning the expected result (

Answer 1

To avoid any partial matches, you must use anchors:

• ^ - start of a string
• $ - end of string.

So use

$pattern = "/^(?:Banana|Apples)$/i";

See demo

Since you have an alternative list, you need to group them so that the anchors apply correctly, not just to the first and last alternatives. If you use "/^Banana|Apples$/i", banana will be matched in bananas and apples in =apples.

To only group alternatives but not store in any capture groups, a non-capturing group can be used ((?:....)). Moreover, you do not need capturing groups set on the entire pattern since the whole match text is always stored inside Group 0.