Question

You want to accept a username that only contains letters, numbers, and underscores. Which PHP code correctly validates this input using filter_var() and a custom pattern?

Accepted Answer

$username = $_POST['username'];
if (filter_var($username, FILTER_VALIDATE_REGEXP, ['options' => ['regexp' => '/^[a-zA-Z0-9_]+$/']])) {
    echo "Valid username";
} else {
    echo "Invalid username";
}

Answer

$username = $_POST['username'];
if (filter_var($username, FILTER_SANITIZE_STRING)) {
    echo "Valid username";
} else {
    echo "Invalid username";
}

Answer

$username = $_POST['username'];
if (filter_var($username, FILTER_VALIDATE_EMAIL)) {
    echo "Valid username";
} else {
    echo "Invalid username";
}

Answer

$username = $_POST['username'];
if (filter_var($username, FILTER_VALIDATE_INT)) {
    echo "Valid username";
} else {
    echo "Invalid username";
}

You want to accept a username that only contains letters, numbers, and underscores. Which PHP code correctly validates this input using filter_var() and a custom pattern?

Step 1: Understand the requirement

Step 2: Use FILTER_VALIDATE_REGEXP with correct pattern

Step 3: Eliminate distractors

Final Answer:

Quick Check:

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