How to verify an input field using php - php

Question

How can I verify that the contact number a user inputs in the contact form is in fact numbers and they are at least 10 numbers? Meaning I want the input field only accept 10 numbers or more and also accept the plus (+) sign. At the moment the php verifies that the all fields are completed and the email correct.
here is the html code:
<div class="contact-form">
<form id="contact-form" action="sendmail.php" method="post" title="Contact Form" role="form">
<div class="col-sm-6">
<div class="form-group">
<label for="contact-name">Full name</label>
<input type="text" name="name" placeholder="Enter your full name..." class="contact-name" id="contact-name">
</div>
<div class="form-group">
<label for="contact-email">Email</label>
<input type="text" name="email" placeholder="Enter your email..." class="contact-email" id="contact-email">
</div>
<div class="form-group">
<label for="contact-number">Contact number</label>
<input type="text" name="number" class="active" id="contact-number" placeholder="Your contact number...">
</div>
</div>
<div class="col-sm-6">
<div class="form-group">
<label for="contact-message">Message</label>
<textarea name="message" placeholder="Your message..." class="contact-message" id="contact-message"></textarea>
</div>
</div>
<div class="col-sm-12 text-center">
<button type="submit" class="btn btn-default sketchFlowPrint" id="submit">Send</button>
</div>
</form>
</div>
here is the php code:
<?php
// Email address verification
function isEmail($email) {
return preg_match('|^[_a-z0-9-]+(\.[_a-z0-9-]+)*#[a-z0-9-]+(\.[a-z0-9-]{2,})+$|i', $email);
};
if($_POST) {
// Enter the email where you want to receive the message
$emailTo = 'example#gmail.com';
$clientName = addslashes(trim($_POST['name']));
$clientEmail = addslashes(trim($_POST['email']));
$number = addslashes(trim($_POST['number']));
$message = addslashes(trim($_POST['message']));
$subject = 'Query from My Domain';
$sendMessage = 'Hi' . "\n\n";
$sendMessage .= $message . "\n\n";
$sendMessage .= 'From: ' . $clientName . "\n";
$sendMessage .= 'Email: ' . $clientEmail . "\n";
$sendMessage .= 'Contact number: ' . $number . "\n";
$array = array();
$array['nameMessage'] = '';
$array['emailMessage'] = '';
$array['numberMessage'] = '';
$array['messageMessage'] = '';
if($clientName == '') {
$array['nameMessage'] = 'Please enter your full name.';
}
if(!isEmail($clientEmail)) {
$array['emailMessage'] = 'Please insert a valid email address.';
}
if($number == '') {
$array['numberMessage'] = 'Please enter a valid contact number.';
}
if($message == '') {
$array['messageMessage'] = 'Please enter your message.';
}
if($clientName != '' && isEmail($clientEmail) && $message != '') {
// Send email
$headers = "From: " . $clientName . ' <' . $clientEmail . '>' . "\r\n";
$headers .= PHP_EOL;
$headers .= "MIME-Version: 1.0".PHP_EOL;
$headers .= "Content-Type: multipart/mixed;".PHP_EOL;
$headers .= " boundary=\"boundary_sdfsfsdfs345345sfsgs\"";
mail($emailTo, $subject, $sendMessage, $headers);
}
echo json_encode($array);
} else {
header ('location: index.html#contact');
}
?>
here is the jQuery:
// Contact form
$('.contact-form form').submit(function(e) {
e.preventDefault();
var form = $(this);
var nameLabel = form.find('label[for="contact-name"]');
var emailLabel = form.find('label[for="contact-email"]');
var numberLabel = form.find('label[for="contact-number"]');
var messageLabel = form.find('label[for="contact-message"]');
nameLabel.html('Full name');
emailLabel.html('Email');
numberLabel.html('Contact number');
messageLabel.html('Message');
var postdata = form.serialize();
$.ajax({
type: 'POST',
url: 'sendmail.php',
data: postdata,
dataType: 'json',
success: function(json) {
if(json.nameMessage !== '') {
nameLabel.append(' - <span class="red error-label"> ' + json.nameMessage + '</span>');
}
if(json.emailMessage !== '') {
emailLabel.append(' - <span class="red error-label"> ' + json.emailMessage + '</span>');
}
if(json.numberMessage !== '') {
numberLabel.append(' - <span class="red error-label"> ' + json.numberMessage + '</span>');
}
if(json.messageMessage !== '') {
messageLabel.append(' - <span class="red error-label"> ' + json.messageMessage + '</span>');
}
if(json.nameMessage === '' && json.emailMessage === '' && json.numberMessage === '' && json.messageMessage === '') {
form.fadeOut('fast', function() {
form.parent('.contact-form').append('<h2 class="text-center"><span class="orange">Thanks for contacting us!</span> We will get back to you very soon.</h2>');
});
}
}
});
});

Answer 1

I'm guessing that the + needs to be the first character (international phone numbers)?
Then this should do it:
if (!preg_match('/^(\+?)+([0-9]{10,})$/', $number)) {
$array['numberMessage'] = 'Please enter a valid contact number.'
}
The plus sign is optional. If it should be required, just remove the ? after the plus sign in the expression.

Answer 2

Check the length is less than 10 or see if the input differs from the filtered input (+ and digits removed).
<?php
function valid_tel($in) {
$valid = true;
if(strlen($in) < 10 || $in !== preg_replace('#[^0-9+]#','', $in)) {
$valid = false;
}
return $valid;
}
var_dump(valid_tel(''));
var_dump(valid_tel('01234'));
var_dump(valid_tel('01234567890')); // 11 long
var_dump(valid_tel('+012345678')); // 10 inc +
var_dump(valid_tel('+0123456'));
var_dump(valid_tel('0123456xyz7890'));
Output:
boolean false
boolean false
boolean true
boolean true
boolean false
boolean false