Check to see if the web given web address is blocking visitors ip

I want to make an web application where a user inputs a web address and click to a submit button. Now what my application does it checks if the given web address is blocking his/her ip address. Can you please help me to make this web application? I want to use php and javascript.

Basic PHP and HTML structure:

<?php
if ( isset( $_POST['check_status'] ) ) {

  $_POST = array_map( 'stripslashes', $_POST );
  extract( $_POST );

  if ( empty( $web_addr ) ) {
    $error = "Web address is required.";
  }

  if ( !isset( $error ) ) {
    function checkIpBlocked() {
      /* I need this code to check */
    }
  }
}
?>

<h2>Check your ip address is blocked or not</h2>
<form action="" method="POST">
  <label for="web_addr">Enter Web Address</label>
  <input type="text" name="web_addr" placeholder="Enter Web Address">
  <input type="hidden" name="user_ip" value="<?php $_SERVER['REMOTE_ADDR']; ?>">
  <input type="submit" name="check_status" value="Check Status">
  <div id="status"><?php if ( isset( $error ) ) { echo $error } ?></div>
</form>

PHP: