How can I get regex to validate php addslashes() characters (specifically apostrophe)

Question

I am trying to validate a string (a name) using preg_match(). I am passing in a string called $lname which is a string containing an apostrophe which has been slashed. An example of this is "O\'Neill". I have tried multiple regex layouts and solutions for this including (\') , \' , and just '. It does not work and give a true output being valid. Can anyone offer a solution.

Here is my code:

$lname = "O\'Neill";
if(preg_match("/^[a-zA-Z\'\s-]+$/",$lname))
    echo "valid";

I see two solutions: 1) accept \ in the regex pattern ; 2) remove \ from your string before testing the regex. — Mistalis, Jun 22 '17 at 13:25
You have to escate the slash with double slash so instead you have to use `[a-zA-Z\\'\s-]+` — Youcef LAIDANI, Jun 22 '17 at 13:26
If you want to allow the slash only before the apostrophe, use `^([a-zA-Z\s-]|\\?')+$` — logi-kal, Jun 22 '17 at 13:29
You just need `"/^[a-zA-Z\\\\'\s-]+$/"`. Better - `"/^[a-zA-Z\\\\'\s-]+\z/"`. Shorter - `"/^[A-Z\\\\'\s-]+\z/i"` — Wiktor Stribiżew, Jun 22 '17 at 14:03
@WiktorStribiżew Possibly, I thought from the first read they don't want to match O'Neil as a way of ensuring slashes were added, but maybe I misunderstood the requirements. — Devon Bessemer, Jun 22 '17 at 14:18
@Devon The question is rather poorly worded. Let Alex explain. Alex? — Wiktor Stribiżew, Jun 22 '17 at 14:19

Devon Bessemer · Answer 1 · 2017-06-22T13:44:07.987

Your first problem is not escaping the backslash. You'd need to write a literal backslash as \\ in regex.

However, if you just do that, you'd be looking for a backslash or apostrophe anywhere, not a sequential \' because of your [...] which matches any character inside.

The correct way to do this would be to look for it outside of the brackets.

^([a-zA-Z\s-]|\\')+$

http://regexr.com/3g7dm

Note: If you're doing this to protect your SQL queries, it's not the proper way. You should be using prepared statements.

How can I get regex to validate php addslashes() characters (specifically apostrophe)

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