Question

I have a problem using preg_match. (I’m very new to regular expressions)

if(preg_match('^/http:\/\/myWebsite\.com\/', $_SERVER['HTTP_REFERER'])) {
return true;
}
else{
return false;
}

Always returns false and it shouldn’t. Where am I wrong?

UPDATE

Hi everybody ! Thanks all of you for your help ! Every check is fine now

Answer 1

Your regular expression is missing the delimiters, as PHP should have warned you:

$_SERVER['HTTP_REFERER'] = 'http://myWebsite.com/foo.html';
var_dump( preg_match('^/http:\/\/myWebsite\.com\/', $_SERVER['HTTP_REFERER']) );

… triggers:

Warning: preg_match(): No ending delimiter

Since you are allowed to choose your own delimiter, it’s simpler to pick one that’s not in the text:

preg_match('@^http://myWebsite\.com/@', $_SERVER['HTTP_REFERER'])

Additionally, if the text is not fixed (not this case I presume), PHP can escape it for you:

preg_match('/^' . preg_quote('http://myWebsite.com/', '/') . '/', $_SERVER['HTTP_REFERER'])

I suggest you configure your development box to display all possible errors. You have several ways to do so:

1. Edit your php.inifile:

   error_reporting = E_ALL | E_STRICT
   display_errors = On
   

2. Put this on top of your script:

   <?php
   
   error_reporting(E_ALL | E_STRICT);
   ini_set('display_errors', TRUE);
   

3. If PHP runs as Apache module, you can also use an .htaccess file:

   # Print E_ALL | E_STRICT from a PHP script to get the appropriate number:
   php_value error_reporting 2147483647
   php_flag display_errors on