Just use all hashing algorithems PHP has available, but select SHA1 by default.

index.php

 <?php
+$methods = hash_algos();
 $hash = null;
 if(isset($_POST['input']) && isset($_POST['type'])) {
 	$input = $_POST['input'];
 	$type = strtolower($_POST['type']);
 
-	if(in_array($type, hash_algos())) {
+	if(in_array($type, $methods)) {
 		$hash = hash($type, $input);
     } else {
 	    $hash = "Not-supported hashing method selected";
@@ -46,11 +47,8 @@ if(isset($_POST['input']) && isset($_POST['type'])) {
 
             <select class="form-control" name="type" id="type">
                 <?php
-                $methods = array(
-                        "sha1", "sha256", "sha384", "sha512", "md2", "md5"
-                );
                 foreach($methods as $method) {
-                    if(isset($_POST['type']) && $method == $_POST['type']) {
+                    if((isset($_POST['type']) && $method == $_POST['type']) || (!isset($_POST['type']) && $method == "sha1")) {
 	                    echo "<option value='$method' selected>$method</option>";
                     } else {
 	                    echo "<option value='$method'>$method</option>";