Regular Expressions in PHP

A Regular Expression (RegEx) is a pattern used to search, match, or validate text.

Why Regular Expressions are Used?

• Validate form inputs
• Check email format
• Validate phone numbers
• Search patterns in strings

Exam Definition: Regular expressions are patterns used for matching and validating strings.

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PHP RegEx Functions

PHP uses PCRE (Perl Compatible Regular Expressions).

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Validating Text Boxes (Name Validation)

Only Alphabets Allowed

$name = "Rohit";

if(preg_match("/^[a-zA-Z ]+$/", $name)){
   echo "Valid Name";
}else{
   echo "Invalid Name";
}

Explanation ^ start $ end [a-zA-Z ] allowed characters + one or more characters

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Validating Email Address

$email = "test@gmail.com";

if(preg_match("/^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+.[a-zA-Z]{2,}$/", $email)){
   echo "Valid Email";
}else{
   echo "Invalid Email";
}

Real-time Use: Login and registration forms.

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Validating Phone Number

10-Digit Mobile Number

$phone = "9876543210";

if(preg_match("/^[0-9]{10}$/", $phone)){
   echo "Valid Phone Number";
}else{
   echo "Invalid Phone Number";
}

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Validating Password

$password = "Test@123";

if(preg_match("/^(?=.*[A-Za-z])(?=.*d)(?=.*[@$!%*#?&]).{6,}$/", $password)){
   echo "Strong Password";
}else{
   echo "Weak Password";
}

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Creating Custom Regular Expressions

Custom RegEx are created using symbols and patterns.

Common RegEx Symbols

Custom Example: Username Validation

Rules

• Letters and numbers only
• Length 5 to 10

$username = "user123";

if(preg_match("/^[a-zA-Z0-9]{5,10}$/", $username)){
   echo "Valid Username";
}else{
   echo "Invalid Username";
}

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Advantages of Regular Expressions

• Fast validation
• Less code
• Accurate matching
• Secure input handling