FILTER_VALIDATE_REGEXP to validate FLOAT data of a variable in PHP

Validate text with a regular expression

FILTER_VALIDATE_REGEXP applies a PCRE pattern supplied through the options array. Keep the pattern anchored when the whole input must match.

$options = ['options' =&gt; ['regexp' =&gt; '/^[A-Z]{2}\d{4}$/']];
var_dump(filter_var('AB1234', FILTER_VALIDATE_REGEXP, $options));

$string = "Welcome to plus2net.com";

var_dump(filter_var($string, FILTER_VALIDATE_REGEXP,
array("options"=&gt;array("regexp"=&gt;"/^W(.*)/"))))

Output is

string(23) "Welcome to plus2net.com"

By using FILTER_VALIDATE_REGEXP we can validate Regular expression .

Change the $string variable value to

$string="ZWelcome to plus2net.com";

Output is now

bool(false)

Example 2

$string = "Welcome to plus2net.com"; // change the first char and see the result

if(filter_var($string, FILTER_VALIDATE_REGEXP,array("options"=&gt;array("regexp"=&gt;"/^W(.*)/")))){
echo "yes Cleared ";	
}else{
echo " No not cleared ";	
}

Output is here

yes Cleared

Example 3: Validating an Email Format with Custom Regex

Although PHP has FILTER_VALIDATE_EMAIL, sometimes custom validation is needed. This example validates an email using a regular expression:

$email = "test@example.com";
$pattern = "/^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/";
if (filter_var($email, FILTER_VALIDATE_REGEXP, array("options" => array("regexp" => $pattern)))) {
    echo "Valid Email";
} else {
    echo "Invalid Email";
}

Example 4: Ensuring Password Strength

We can use a regex to ensure a password contains at least one uppercase letter, one lowercase letter, one digit, and is at least 8 characters long.

$password = "Password123";
$pattern = "/^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)[a-zA-Z\d]{8,}$/";
if (filter_var($password, FILTER_VALIDATE_REGEXP, array("options" => array("regexp" => $pattern)))) {
    echo "Password is strong.";
} else {
    echo "Password is weak.";
}

Example 5: Validating URLs with Specific Domain

This example validates URLs ( php has FILTER_VALIDATE_URL) that are specific to a certain domain, like *.com domains:

$url = "https://www.example.com";
$pattern = "/^https?:\/\/(www\.)?([a-z0-9]+)\.com$/i";
if (filter_var($url, FILTER_VALIDATE_REGEXP, array("options" => array("regexp" => $pattern)))) {
    echo "Valid URL";
} else {
    echo "Invalid URL";
}

Filter reference Validating Boolean data Ctype_alnum to check alphanumeric characters Validating Email address

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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