PHP preg_match() or strpos to check if string starts with substring

问题

I am changing views of a page depending the $_GET['code'] it can equal a series of different codes but they will all start with either Red, Town or Bearing, then a series of characters.

For example, the following would all trigger the condition

RedWings-223123-NY
Townmansion-2341322-KY
BearingWays-23422-DC

I have tried

<?php if(preg_match("%(?=.*Bear)(?=.*Red)(?=.*Town)%", $_GET['code'])): ?>

   <span> new view </span>

<?php endif ?>

and

<?php if( strpos($_GET['code']), "Red" ) !== false) || strpos($_GET['code']), "Bear" ) !== false || strpos($_GET['code']), "Town" ) !== false)): ?>

   <span>new view</span>

<?php endif ?>

回答1:

Your strpos is incorrect syntactically, you close the functions before passing the term to search for.

Your regex requires all terms be present and doesn't check for the start of the string. You need to use an or and a leading anchor. This:

^(?:Bear|Town|Red)

should do it.

Regex Demo: https://regex101.com/r/civdig/3/

Correct strpos usage:

<?php if( strpos($_GET['code'], "Red" ) === 0 || strpos($_GET['code'], "Bear" ) === 0 || strpos($_GET['code'], "Town" === 0)): ?>

   <span>new view</span>

<?php endif ?>

You need the 0 to confirm it matches, otherwise you are checking that it is somewhere in there.

来源：https://stackoverflow.com/questions/47207338/php-preg-match-or-strpos-to-check-if-string-starts-with-substring