Numeric input validation in PHP

Question

I'm trying to validate an input for Account number in php form. It should contain 8 numbers and '-' optionally. If there is '-' - it should be ignored. After pressing the Submit button, the warning message suppose to be displayed above the form in case input is invalid.

Please help.

This is what I got so far, but I'm not sure if this is correct and don't know how to display a warning message above the form.

$acctnum= "$acctnum";

if(empty($acctnum)){
  echo "You did not enter an account number, please re-enter"; }

else if(!preg_match("\-^[0-9]{8}", $acctnum)){
  echo "Your account number can only contain eight numbers. Please re-enter."; }

Thank you!

Can you guarantee that all your accounts will have exactly eight digits in the future? — yunzen
– yunzen, Commented Nov 18, 2012 at 21:18
the condition of an assignment is that account number has to have exactly 8 digits — Oksana
– Oksana, Commented Nov 18, 2012 at 23:24

Niet the Dark Absol · Accepted Answer · 2012-11-18 20:57:32Z

2

You don't appear to be trying. No documentation or tutorial will tell you to make a Regex like that. For starters, where are the delimiters? Why is - escaped when it's outside a character class and therefore has no special meaning? What is that ^ doing there?

This should do it:

$acctnum = str_replace("-","",$acctnum);
if( !preg_match("/^\d{8}$/",$acctnum)) echo "Error...";

answered Nov 18, 2012 at 20:57

Niet the Dark Absol

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3 Comments

mario Over a year ago

This will strip multiple -, not allow just one. Might be better to use an assertion here. But OP possibly just meant optional at the start(?)

Oksana Over a year ago

Thank you! It should strip multiple '-'.

Oksana Over a year ago

Kolink, thank you! I actually tried many other options. The one I wrote is just one of them. I didn't think about str_replace(), didn't use delimiters.

sh03 · Accepted Answer · 2012-11-18 21:08:37Z

0

Since regex are quite expensive I'd go like that instead:

$acctnum = (int) $acctnum; // this automatically ignore the '-'
if ($acctnum < 0) $acctnum = -$acctnum;
$digits = ($acctnum == 0) ? log10($acctnum) + 1 : 1;
if ($digits === 8) { ... }

edited Nov 18, 2012 at 21:08

answered Nov 18, 2012 at 21:02

sh03

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2 Comments

yunzen Over a year ago

I don't think we will have performance issues with the regex for this simple task. And it would be more readable than your code. And what about leading zeros?

sh03 Over a year ago

@yunzen, Since no one told me that there could be any and considering that $acctnum seems a counting integer this solution is faster. If it's not the OP solution at least I'll leave it here for future viewers.

yunzen · Accepted Answer · 2012-11-18 21:12:52Z

0

Split the task in two. First get rid of the "-" with str_replace and then check for the numbers.

$match = preg_match("/^\d{8}$/", str_replace("_", "", $str));
if ($match > 0) {
    // Correct
} else {
    // incorrect
}

answered Nov 18, 2012 at 21:12

yunzen

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