simple regular expression in php to check for possible values for a variable

Question

There are are a few finite values that my variable $_GET['action'] can take, either "new", "edit", or "delete".

I want to sanitize my input for security and make sure the variable is only one of those above values, how can I do that using regular expressions?

I don't want to go and say:

if(isset($_GET['action']) && ($_GET['action'] == 'new' || $_GET['action'] == 'edit' || $_GET['action'] == 'delete'))

I recommend to make a function of it. This way you are more flexible. — MKroeders
– MKroeders, Commented May 19, 2013 at 14:22

hek2mgl · Accepted Answer · 2013-05-19 14:24:04Z

5

I would not use a regex for this. Use in_array() to check a value against a white list:

if(!in_array($_GET, array("new", "edit", "delete"), TRUE)) {
    die('Error!');
}

answered May 19, 2013 at 14:24

hek2mgl

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5 Comments

user961627 Over a year ago

why? would regex be slower?

hek2mgl Over a year ago

I expect a regex is much slower. Will test, give me a minute

kero Over a year ago

Is the strict flag necessary?

hek2mgl Over a year ago

@kingkero Good question! :) In this special case: not. However, I suggested it in the example, as the real data might be sensitive for it

hek2mgl Over a year ago

@user961627 My little test showed me that in_array() is ~ 30% faster then preg_match()

kero · Accepted Answer · 2013-05-19 14:21:42Z

2

A switch is probably the best solution, but seeing nothing of your code makes it hard to tell. The regex you are searching for looks like the following

/^(new|edit|delete)$/i

Described in words it checks if between the beginning and the end of the line there is one of the three possibilities (case insensitive)

answered May 19, 2013 at 14:21

kero

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1 Comment

Carlo Moretti Over a year ago

agree with this, regex should be more of a pattern recongition than a simple value checker

Skatox · Accepted Answer · 2013-05-19 14:23:11Z

2

It's simple just do:

if( isset($_GET['action']) && preg_match("/^(new|edit|delete)$/i", $_GET['action']))
     doSomething();

answered May 19, 2013 at 14:23

Skatox

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Comments

Ejaz · Accepted Answer · 2013-05-19 14:22:06Z

1

this should help

if(isset($_GET['action']) && in_array($_GET['action'], array('new', 'edit', 'delete')))

or

$allowed_methods = array('new', 'edit', 'delete');
if(isset($_GET['action']) && in_array($_GET['action'], $allowed_methods))

answered May 19, 2013 at 14:22

Ejaz

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Comments

Patrice Levesque · Accepted Answer · 2013-05-19 14:22:38Z

1

Match them using the or (|) operator

if (preg_match("/^(new|edit|delete)$/", $_GET['action'])) { ...

answered May 19, 2013 at 14:22

Patrice Levesque

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Comments

Sam · Accepted Answer · 2013-05-19 14:35:34Z

1

if(isset($_GET['action'])){
  switch($_GET['action']){
    case 'edit':
        //etc...
        break;
    case 'new':
        //etc...
        break;
    case 'delete':
        //etc...
        break;
    default:
        echo 'No valid actions';
  }
}

Use the switch for a good action management

edited May 19, 2013 at 14:35

answered May 19, 2013 at 14:29

Sam

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2 Comments

kero Over a year ago

Then you need to change your code twice if you want to add/remove actions

Sam Over a year ago

@kingkero in effects was useless the first control, the switch is enough

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