正则表达式：替换单词，除非后跟破折号

Question

How to replace "cat" in a given string by "FELIX" but not if it's followed by special character like "- or _ or :"

example :

"my cat is hungry all the time" => "my Felix is hungry all the time"

"the products cat-1547 and cat:154 are disponible now" => "the products cat-1547 and cat:154 are disponible now"

thanks

Answer 1

Use a negative lookahead together with word boundaries:

/\bcat\b(?![-:])/

See the regex demo

Pattern explanation:

• \b - leading word boundary (to avoid matching cat in tomcat)
• cat - a literal string cat
• \b - trailing word boundary (i.e. the next char must be a non-letter, non-digit and non-underscore character, and it prevents from matching cat in catwalk)
• (?![-:]) - a negative lookahead that fails the match if a - or : immediately follows the cat.

PHP demo:

$re = '~\bcat\b(?![-:])~'; 
$str = "my cat is hungry all the time
the products cat-1547 and cat:154 are disponible now"; 
$subst = "Felix"; 
$result = preg_replace($re, $subst, $str);
echo $result;