Anchored regex without fear

preg_match

Function preg_match tests a string against a pattern and returns 1 on success and 0 on failure. Anchors lock the test to the full string so partial hits do not pass.

Caret marks the start and dollar marks the end, so a pattern with both checks the whole value from first to last character.

$text = "order-42"; if (preg_match("/^order-[0-9]+$/", $text, $m)) { echo $m[0]; }

preg_replace

Function preg_replace returns a new string with every match replaced. The original value stays unchanged and the result holds the edits.

Use a character class for digits or letters when the exact text varies but the shape stays the same.

$text = "hi 2026-10-06"; echo preg_replace("/[0-9]+/", "#", $text);

Delimiters

Every pattern needs delimiters around the core expression. The common choice is / but hash and tilde work the same way.

Pick a delimiter that does not appear in the pattern itself. That choice keeps the pattern short and easy to read.

$text = "path to file"; var_dump((bool) preg_match("#^path#", $text)); var_dump((bool) preg_match("~file$~", $text));

Escape with preg_quote

Never paste user text straight into a pattern because dots and brackets have special meaning. Function preg_quote escapes every special character for you.

Pass the delimiter as the second argument so it gets escaped as well, then add anchors around the quoted part.

$word = "price (usd)"; $pattern = "/^" . preg_quote($word, "/") . "$/"; $text = "price (usd)"; var_dump((bool) preg_match($pattern, $text));

Next: Multibyte strings

Article author: Arthur Isaev