Variables and Regex

[oracle259]

Hi
I need to know to what extent can we use variable with regex e.g.

is it possible to do this:

$var1 = "abc.gov.jm";
$var2 = "defg.gov.au";

/^(?=.*?[a-zA-Z])(?:[a-zA-Z][0-9\-\.\_]?)+@(?:$var1|$var2)$/

or if not what is the best way of achieving the same thing

[shoz]

[quote=oracle259]
Hi
I need to know to what extent can we use variable with regex e.g.

is it possible to do this:

$var1 = "abc.gov.jm";
$var2 = "defg.gov.au";

/^(?=.*?[a-zA-Z])(?:[a-zA-Z][0-9\-\.\_]?)+@(?:$var1|$var2)$/

or if not what is the best way of achieving the same thing
[/quote]
Remember that the regex is a string, and you can create that string just as you would any other string in PHP.
[code]
$var = 'l';
$regex = "/^$var\$/";

//or
$regex = '/^'.$var.'$/';

//or
$regex = "/^{$var}\$"/;
[/code]
The regex would be '/^l$/'. Although the "$" symbol at the end of the regex doesn't need to be escaped in this example, I think it's good practice to escape it when it's inside double quotes to be clear.

It should also be considered good practice to surround any var that's "touching" other characters with "{}". Again, although not necessary in every situation is required in some for clarity.

http://www.php.net/manual/en/language.types.string.php

[effigy]

Follow the same interpolation rules as PHP, just be aware that you may need to pass your variable through preg_quote first. The periods in your example "abc.gov.jm" are not literal periods in regex.

[shoz]

[quote=effigy]
pass your variable through preg_quote first
[/quote]
Agreed. I'd say that's the more important thing to remember.