Removing (nearly) all non-numeric characters from a string

Question

So I've created a number format generator which will take human telephone numbers, and apply the appropriate format following the HSCIC Rules and Regulations, one issue I'm having is number validation.

For instance, I get to a step, just after removing all whitespace, and I'd like to check the number once more, removing every character except: Numbers: 0 - 9 Letters: E, X, T - case insensitive Special: +, :

I've looked online but I can't find a way to only keep these few characters. All help is appreciated!

DaTebe · Accepted Answer · 2016-06-27 09:09:40Z

2

If I understand you correctly you can use this:

$re = "/[0-9XxTtEe+:]*/"; 
$str = "394160etg9834ztg";  // <-- User Input

preg_match_all($re, $str, $matches);

In $matches should be all characters that are allowed. Just combine the results that are matched in $matches

answered Jun 27, 2016 at 9:09

DaTebe

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5 Comments

Jamie Belcher Over a year ago

I'm trying to make sense of this function, I tend to steer clear of preg_match, so how does the $re work? And should $matches be an array?

DaTebe Over a year ago

$re is the regular expression applied on the input string. It matches all charcters from 0-9 and your special characters (The matching is done in preg_match_all). $matches is an "Array of all matches in multi-dimensional array ordered according to flags". Try a var_dump($matches) to see what datastructure is behind it and then work with the result.

Jamie Belcher Over a year ago

I var dumped the area and I see it's split at each incorrect value, so naturally I'm attempting to implode the area to create it into a single string. But I'm being hit with the error "Error converting array to string on line XXX"

DaTebe Over a year ago

Try implode('', $matches[0]). For me the results where in index 0.

Jamie Belcher Over a year ago

Yeah that was my mistake, I didn't notice it created two arrays! It's all working thank you! I'll mark this as the answer

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