Regular expression match multiple substring

Question

I have written a regular expression to test how a string is a logical expression or not. Here is the regular expression:

/(.*)(<|>|<=|>=|=|!=)(.*)/

And here is the subject which I tested with the expression above:

3!=2

The preg_match_all function in PHP return the following array:

[
  [
    "3!=2"
  ],
  [
    null
  ],
  [
    "="
  ],
  [
    "2"
  ]
]

I got a wrong logical operator because it's not match only the = pattern but also match the != operator. How should I rewrite the regular expression to not match multiple strings in the brackets?

Answer 1

You should exclude <>! before the operator and = after operator. Then, just to shorten, group the operators tighter.

([^<>!]*)([<>]=?|!?=)([^=]*)

You could also shorten it a bit with this:

(\w+)([<>]=?|!?=)(\w+)

---

With <=>, use

([^<>!]*)(<=>|[<>]=?|!?=)([^=>]*)

or, better yet in some cases,

(\w+)(<=>|[<>]=?|!?=)(\w+)