language: PHP (php 5.4.4)
date: 412 days 4 hours ago
link:
visibility: public 
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<?php
 
function is_valid_regex($pattern)
{
    return is_int(@preg_match($pattern, ''));
}
 
$patterns = array('/[[0-9]/i', '//(.*)/', '/(.*)-(.*)-(.*)/ ', '/([a-z]+)-([0-9_]+)/i');
 
foreach ($patterns as $pattern)
{
    echo sprintf('%s is %b' . "\n", $pattern, is_valid_regex($pattern));
}