PHP form validation function

Question

I am currently writing some PHP form validation (I have already validated clientside) and have some repetitive code that I think would work well in a nice little PHP function. However I am having trouble getting it to work. I'm sure it's just a matter of syntax but I just can't nail it down.

Any help appreciated.

//Validate phone number field to ensure 8 digits, no spaces.
if(0 === preg_match("/^[0-9]{8}$/",$_POST['Phone']) {
    $errors['Phone'] = "Incorrect format for 'Phone'";
}

if(!$errors) {
    //Do some stuff here....
}

I found that I was writing the validation code a lot and I could save some time and some lines of code by creating a function.

//Validate Function
function validate($regex,$index,$message) {
    if(0 === preg_match($regex,$_POST[$index])) {
        $errors[$index] = $message;
    }

And call it like so....

validate("/^[0-9]{8}$/","Phone","Incorrect format for Phone");

Can anyone see why this wouldn't work?

Note I have disabled the client side validation while I work on this to try to trigger the error, so the value I am sending for 'Phone' is invalid.

I believe that you would need curly braces for php to evaluate the variable index if contained between single quotes. Like so, $_POST['{$index}'] — Matt
– Matt, Commented Dec 19, 2012 at 5:10
@Matt: that's not needed. If the param is a string, it will work just fine with $_POST[$index] — gview
– gview, Commented Dec 19, 2012 at 5:12
There are lots of reasons this doesn't work, not the least of which is your example doesn't make any sense. If this is a function, then you would want to return a value, which you don't. If you also want to set an array to the error message value, then that parameter has to be passed into the function by reference. — gview
– gview, Commented Dec 19, 2012 at 5:17

gview · Accepted Answer · 2012-12-19 05:35:21Z

4

Let's try something a little more thought out.

You want to use this like so:

if (validate(...)) {
    // It's ok
}

Then I'd suggest this:

function validate($regex, $index, $message, &$errors) {     
    if (isset($_POST[$index]) && 1 === preg_match($regex, $_POST[$index])) {
        return true;            
    }
    $errors[$index] = $message; 
    return false;        
}

Now you have an opportunity to dump out of validation on error, or you can chain through these passing in the $errors and fill it with validation errors. No globals used.

edited Dec 19, 2012 at 5:35

answered Dec 19, 2012 at 5:29

gview

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1 Comment

Barbs Over a year ago

Hi gview, thanks this looks promising. I want to process the form whenever the $errors array is empty. If the array contains error messages I just want to display the errors to the user for now. If I just check if the validate returns true won't I have to perform this check for every function call? I thought I could check every field that needs validation, then check if the form validated as a group (by simply checking the $errors array) before going to the database. Or am I misunderstanding something?

Brian Duncan · Accepted Answer · 2012-12-19 05:36:47Z

1

Here's a fix:

//Validate Function
function validate($regex,$index,$message) {
    global $errors;
    if(0 === preg_match($regex,$_POST[$index])) {
        $errors[$index] = $message;
    }
}

Here's the issue:

if(0 === preg_match($regex,$_POST[$index],$message)

$message, a string, is where an array of matches is supposed to go. You don't need it.

From the manual: int preg_match ( string $pattern , string $subject [, array &$matches [, int $flags = 0 [, int $offset = 0 ]]] )

http://php.net/manual/en/function.preg-match.php

edited Dec 19, 2012 at 5:36

answered Dec 19, 2012 at 5:11

Brian Duncan

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3 Comments

gview Over a year ago

Functionally this does the job, but I'm not a fan of the use of global, even though I understand you are just trying to answer the question based on the original code snippet.

Brian Duncan Over a year ago

Yup, I'm also not a big fan of using global. But then again I'm also not a big fan of one-size fits all validation functions.

gview Over a year ago

agreed. Also so many options out there (symfony2 validate component, ZF2 Validate class.

RisingSun · Accepted Answer · 2012-12-19 05:30:54Z

0

You are missing a closing parentheses at of your if of your validate function Change this

if(0 === preg_match($regex,$_POST[$index],$message)

To this

if(0 === preg_match($regex,$_POST[$index],$message))

answered Dec 19, 2012 at 5:30

RisingSun

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1 Comment

Barbs Over a year ago

thanks. Typo when I reproduced the function here. Fixed up top.

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