Use of all patterns

All patterns explained in this tutorial can be used by using the preg_match function, for example using an if loop:

//$value = $_POST['input_field_name']; for example
if(preg_match("/pattern/", $value))
   //matched
else
  //did not match

Email Validation

To validate a user input for an email, to check whether it’s a valid email, can be done in several ways. Here I’ll be showing 2 ways to validate an email. To create a pattern for validating an email you’ll first need to think of how an email can look like ( structure ). Which is:

email_name@email_provider.lang

Where ‘lang’ can be anything like: com or net or nl ( dutch ), etc.. The ‘email_name’ can be anything of any length containing alphabetical characters, numbers or the – _ symbols. Same goes for the ‘email_provider’. So for validating USA email addresses (.com) for example, we could have a pattern like this:

Pattern:

/^[A-Za-z0-9-_.]*@[A-Za-z0-9-_.]*(\.com)$/

However this pattern will only allow/match email addresses that end with .com. We could use the | seperator to allow several ‘extensions’ for the email ( .com OR .net OR .nl, etc..). That would look like this:

Pattern:

/^[A-Za-z0-9-_.]*@[A-Za-z0-9-_.]*(\.com|\.net|\.nl|\.de|\.be|\.co\.uk)$/

And you could add all extensions you want to allow for the email address there, seperated by | and don’t forget to escape the dots (.) with a backslash (\) so it will be treated as a normal character.

Note: a second way to do this could be to allow all extensions (.com, .net or .anythinghere). To do this just replace the \.com|\.net|etc… by \.[A-Za-z0-9]* which basicly means: all alphabetical characters and numbers.

Example of use:

<?php

$email = "validemail123@validprovider_09.net";

if(preg_match("/^[A-Za-z0-9-_.]*@[A-Za-z0-9-_.]*(\.com|\.net|\.nl|\.de|\.be|\.co\.uk)$/", $email)) {

    echo "<p> Valid email: {$email} </p>";

}else{

    echo "<p> Invalid email: {$email} </p>";

}

$email = "invalid' email@invalid,provider}.fpweo";

if(preg_match("/^[A-Za-z0-9-_.]*@[A-Za-z0-9-_.]*(\.com|\.net|\.nl|\.de|\.be|\.co\.uk)$/", $email)) {

    echo "<p> Valid email: {$email} </p>";

}else{

    echo "<p> Invalid email: {$email} </p>";

}

?>

Output:

Valid Email: validemail123@validprovider_09.net

Invalid Email: invalid’ email@invalid,provider}.fpweo

Website Address Validation

For creating a pattern to validate website adresses (urls) we’ll have a look at a valid structure of a website address first, which is similar to:

http(s)://(www. or subdomain.)websitename.com(/directories)(/page.ext)(?getvar&getvars)

Where what’s between brackets is optionally. The .com can be any other ‘extension’ of course (.net or .co.uk, etc.).

Pattern:

/^(http)(s)?(:\/\/)(www\.|[A-Za-z0-9_-]*\.)?[A-Za-z0-9_-]*(\.com|\.net|\.co\.uk|\.net)(\/|\/[A-Za-z0-9-_ .]*)*$/

This is just an example of a pattern I created that could be used. It may at first look complex but it isn’t that complex at all if you have a further look into it. Let’s go through it briefly. Each valid website address starts with ‘http’ (^(http)) followed by an optional ’s’ ( (s)? ). After that there’s a ‘://’ which is put inside the pattern as (:\/\/) as all /s need to be escaped by a \. So // becomes \/\/. Then there’s an optional ( so a ? behind the collection ) ‘www.’ or ’subdomain_name.’ where the subdomain_name can be any alphabetical character or number or _ or – ([A-Za-z0-9_-]) and any size (* = any amount of characters). The question mark behind this collection ( www. | subdomain. ) defines it may occur one or zero times (that it’s optional). Then there’s again the [A-za-z0-9_-] which again means any alphabetical characters or numbers or the _ or – symbol, which is for the domainname of the website which may contain any of these characters in any length (*). Then it should be followed by any of these ‘extensions’ ( \.com|\.net|\.co\.uk|\.net ). Now the rest of the pattern is optional – there can be anything after the url (after a backslash / ).

Example of use:

<?php

$url = "http://www.validurl.net/anypath/anyfile.php?anything";

if(preg_match("/^(http)(s)?(:\/\/)(www\.|[A-Za-z0-9_-]*\.)?[A-Za-z0-9_-]*(\.com|\.net|\.co\.uk|\.net)(\/|\/[A-Za-z0-9-_ .]*)*$/", $url)) {

    echo "<p> Valid url: {$url} </p>";

}else{

    echo "<p> Invalid url: {$url} </p>";

}

$url = "http://invalidurl-^.";

if(preg_match("/^(http)(s)?(:\/\/)(www\.|[A-Za-z0-9_-]*\.)?[A-Za-z0-9_-]*(\.com|\.net|\.co\.uk|\.net)(\/|\/[A-Za-z0-9-_ .]*)*$/", $url)) {

    echo "<p> Valid Url: {$url} </p>";

}else{

    echo "<p> Invalid Url: {$url} </p>";

}

?>

Output:

Valid Url: http://www.validurl.net/anypath/anyfile.php?anything

Invalid Url: http://invalidurl-^.

Note: To only allow domain names website addresses without any paths behind it ( like: http://www.google.com ) remove the last part of the pattern between brackets followed by a * ( which is: (\/|\/[A-Za-z0-9-_ .]*)* ) or replace it by (\/)? if you do want to allow a possible ending backslash ( http://www.google.com/ ).