so lost on simply regex expression

[M.O.S. Studios]

i using regex in a simple function.

 

bascily i need to know if the value fits the following 2 criteria.

 

1. the first character is a + or -

2. the rest of the string is nothing but digits (only numbers, no decimals or other punctuation).

 

 

this is what i tried

 

([+-]{1})([0-9])

 

the problem is it only checks the frst two characters, so this would pass '+1helloworld'.

 

can any one help?

[Pikachu2000]

Is the sign required, or is it safe to assume that if there is no negative sign, the number is positive?

[M.O.S. Studios]

Good question, it has to have one of three values, + then number, - then number, or jut a number. I was gong to use other means to check the latter. But now that I think of it it makes more scene to check all three right  away.

[Adam]

You can use: ^(-|+)?[0-9]+$

[M.O.S. Studios]

didn't work, but this did.

^([-+]|\d)((?![^0-9])[0-9])+$

 

for those of who found this while trying to do something similar I'll explain why.

 

^means see if the first fist this [-+]|\d. (brackets are added to mark what is included in the ^ command).

[-+]|\d means the assigned search has to be + - or  a number.

then there is this.

((?![^0-9])[0-9])+$

(?![^0-9])[0-9]) means make sure there is no characters that are not between the numbers between 0 and 9.

then +$ means start from the end and check until it is false.

 

 

i hope this is clear. and if anyone see that i didn't explain it properly let me know!

[Adam]

My mistake, just forgot to escape the plus. Although can make it simpler, as you kind of did, by using block brackets for matching the plus/minus:

 

var_dump(preg_match('/^[-+]?[0-9]+$/', '-123456')); // returns 1

The pattern you came up with though is just making it more complicated than it needs to be.

[salathe]

A simple alternative would be /^[-+]?\d+$/D  which would match: one or more decimal digits optionally preceded by either a plus or a minus character.  The D pattern modifier is used to disallow a newline (e.g. "12345\n") which the other suggested ones would allow.