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Master in Regular Expressions.

Regular expression can be explained as a pattern that can match various text strings. Using regular expressions you can find (and replace) certain text patterns, for example “all the words that begin with the letter A” or “find only telephone numbers”. Regular expressions are often used in validation classes, because they are a really powerful tool to verify e-mail addresses, telephone numbers, street addresses, zip codes, and more.

In this tutorial I will show you how regular expressions work in PHP, and give you a short introduction on writing your own regular expressions. I will also give you several example regular expressions that are often used.Regular Expressions in PHP
Using regex (regular expressions) is really easy in PHP, and there are several functions that exist to do regex finding and replacing. Let’s start with a simple regex find.

<?php

// Example string

$str = "Let's find the stuff <here>in between</here> these two previous brackets";

// Let's perform the regex

$do = preg_match("/<here>(.*)</here>/", $str, $matches);

// Check if regex was successful

if ($do = true) {

// Matched something, show the matched string

echo htmlentities($matches['0']);

// Also how the text in between the tags

echo '<br />' . $matches['1'];

} else {

// No Match

echo "Couldn't find a match";

}

?>

More expressions

//Credit card: All major cards
'^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14}|6011[0-9]{12}|3(?:0[0-5]|[68][0-9])[0-9]{11}|3[47][0-9]{13})$'

//Credit card: American Express
'^3[47][0-9]{13}$'

//Credit card: Diners Club
'^3(?:0[0-5]|[68][0-9])[0-9]{11}$'

//Credit card: Discover
'^6011[0-9]{12}$'

//Credit card: MasterCard
'^5[1-5][0-9]{14}$'

//Credit card: Visa
'^4[0-9]{12}(?:[0-9]{3})?$'

//Credit card: remove non-digits
'/[^0-9]+/'

//Email address
//Use this version to seek out email addresses in random documents and texts.
//Does not match email addresses using an IP address instead of a domain name.
//Does not match email addresses on new-fangled top-level domains with more than 4 letters such as .museum.
//Including these increases the risk of false positives when applying the regex to random documents.
'\b[A-Z0-9._%-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b'

//Email address (anchored)
//Use this anchored version to check if a valid email address was entered.
//Does not match email addresses using an IP address instead of a domain name.
//Does not match email addresses on new-fangled top-level domains with more than 4 letters such as .museum.
//Requires the "case insensitive" option to be ON.
'^[A-Z0-9._%-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$'

//Email address (anchored; no consecutive dots)
//Use this anchored version to check if a valid email address was entered.
//Improves on the original email address regex by excluding addresses with consecutive dots such as john@aol...com
//Does not match email addresses using an IP address instead of a domain name.
//Does not match email addresses on new-fangled top-level domains with more than 4 letters such as .museum.
//Including these increases the risk of false positives when applying the regex to random documents.
'^[A-Z0-9._%-]+@(?:[A-Z0-9-]+\.)+[A-Z]{2,4}$'

//Email address (no consecutive dots)
//Use this version to seek out email addresses in random documents and texts.
//Improves on the original email address regex by excluding addresses with consecutive dots such as john@aol...com
//Does not match email addresses using an IP address instead of a domain name.
//Does not match email addresses on new-fangled top-level domains with more than 4 letters such as .museum.
//Including these increases the risk of false positives when applying the regex to random documents.
'\b[A-Z0-9._%-]+@(?:[A-Z0-9-]+\.)+[A-Z]{2,4}\b'

//Email address (specific TLDs)
//Does not match email addresses using an IP address instead of a domain name.
//Matches all country code top level domains, and specific common top level domains.
'^[A-Z0-9._%-]+@[A-Z0-9.-]+\.(?:[A-Z]{2}|com|org|net|biz|info|name|aero|biz|info|jobs|museum|name)$'

//Email address: Replace with HTML link
'\b(?:mailto:)?([A-Z0-9._%-]+@[A-Z0-9.-]+\.[A-Z]{2,4})\b'