Contact Form 7 Validate Minlength - php

Question

first of all I'm using latest WordPress and CF7 version. I want to include the minlength validation for the tel field before. I know the syntax minlength=""
can be used inside the CF7, but for unknown reason, it won't work. Only maxlength="" is ok.
I already contacted the plugin support, but seems like no further response. So, I search here and found some code and I edit it so that the field will return an error if user put less than 10 characters. I put the codes inside functions.php
function custom_phone_validation($result,$tag){
$type = $tag['type'];
$name = $tag['name'];
if($name == 'Subject'){
$phoneNumber = isset( $_POST['phonenumber'] ) ? trim( $_POST['phonenumber'] ) : '';
if($phoneNumber < "9"){
$result->invalidate( $tag, "phone number is less" );
}
}
return $result;
}
add_filter('wpcf7_validate_tel','custom_phone_validation', 10, 2);
add_filter('wpcf7_validate_tel*', 'custom_phone_validation', 10, 2);
The result now is, it always display the "phone number is less" even though I insert more than 9 characters. May I know what wrong and how to solve it?

Answer 1

as I've tested you must have your tel field [tel* phonenumber tel-503] where phonenumber is name of postfield you are posting, second issue in your code is $name=='Subject' as you are validating tel so $name will be phonenumber. So it will be like this:
function custom_phone_validation($result,$tag){
$type = $tag['type'];
$name = $tag['name'];
if($name == 'phonenumber'){
$phoneNumber = isset( $_POST['phonenumber'] ) ? trim( $_POST['phonenumber'] ) : '';
if(strlen($phoneNumber) < 9){
$result->invalidate( $tag, "phone number is less" );
}
}
return $result;
}
add_filter('wpcf7_validate_tel','custom_phone_validation', 10, 2);
add_filter('wpcf7_validate_tel*', 'custom_phone_validation', 10, 2);

Answer 2

Your $phoneNumber is a string. You will need to get the length of the string to compare with 9.
Your code will become:
function custom_phone_validation($result,$tag){
$type = $tag['type'];
$name = $tag['name'];
if($name == 'Subject'){
$phoneNumber = isset( $_POST['phonenumber'] ) ? trim( $_POST['phonenumber'] ) : '';
if(strlen($phoneNumber) < 9){//<=====check here
$result->invalidate( $tag, "phone number is less" );
}
}
return $result;
}
add_filter('wpcf7_validate_tel','custom_phone_validation', 10, 2);
add_filter('wpcf7_validate_tel*', 'custom_phone_validation', 10, 2);