Common validation patterns in PHP

Introduction

Validation helps check if data is correct before using it. It stops mistakes and keeps programs safe.

When a user fills a form and you want to check if the email looks right.

When you want to make sure a password is strong enough.

When you need to confirm a number is within a certain range.

When you want to check if a required field is not empty.

When you want to verify a date is in the correct format.

Syntax

PHP

<?php
// Example of validating an email
if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
    // valid email
} else {
    // invalid email
}
?>

Use PHP's built-in filter_var function for common validations like email and URL.

You can use regular expressions with preg_match for custom patterns.

Examples

This checks if the email is in a correct format.

PHP

<?php
// Validate email
$email = '[e-mail]';
if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
    echo 'Valid email';
} else {
    echo 'Invalid email';
}

This checks if a number is between 18 and 99.

PHP

<?php
// Validate number range
$age = 25;
if ($age >= 18 && $age <= 99) {
    echo 'Age is valid';
} else {
    echo 'Age is invalid';
}

This checks if the name is not empty.

PHP

<?php
// Validate non-empty string
$name = 'John';
if (!empty($name)) {
    echo 'Name is provided';
} else {
    echo 'Name is missing';
}

This checks if the phone number matches the pattern 123-456-7890.

PHP

<?php
// Validate pattern with regex
$phone = '123-456-7890';
if (preg_match('/^\d{3}-\d{3}-\d{4}$/', $phone)) {
    echo 'Phone number is valid';
} else {
    echo 'Phone number is invalid';
}

Sample Program

This program checks if the email is correct, password is at least 8 characters, and age is between 18 and 99.

PHP

<?php
// Sample program to validate user input
$email = '[e-mail]';
$password = 'Pass1234';
$age = 20;

// Validate email
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
    echo "Email is invalid\n";
} else {
    echo "Email is valid\n";
}

// Validate password length
if (strlen($password) < 8) {
    echo "Password too short\n";
} else {
    echo "Password length is okay\n";
}

// Validate age range
if ($age < 18 || $age > 99) {
    echo "Age is invalid\n";
} else {
    echo "Age is valid\n";
}

Important Notes

Always sanitize data before validating to avoid security issues.

Use built-in PHP filters when possible for simplicity and reliability.

Regular expressions are powerful but can be tricky; test them carefully.

Summary

Validation checks if data is correct before using it.

Use filter_var for common checks like email and URL.

Use preg_match for custom pattern checks.