Added data type validation passed to bind method

lib/Stmt.php

@@ -86,6 +86,10 @@ public function bind($paramId, $data) {
             $i = reset($array);
         }
 
+        if (!is_scalar($data) && !(is_object($data) && method_exists($data, '__toString'))) {
+            throw new \InvalidArgumentException("Data must be scalar or object that implements __toString method");
+        }
+
         do {
             $realId = -1;
             while (isset($this->named[++$realId]) || $i-- > 0) {

test/Mysql/StmtTest.php

@@ -0,0 +1,69 @@
+<?php
+
+use Amp\Mysql\Stmt;
+use PHPUnit\Framework\TestCase;
+use Amp\Mysql\ResultProxy;
+
+class StmtTest extends TestCase
+{
+    protected $processor;
+    protected $resultProxy;
+
+    public function setUp()
+    {
+        $this->processor = $this->prophesize('Amp\Mysql\Processor');
+        $this->resultProxy = new ResultProxy();
+    }
+
+    /**
+     * @dataProvider provideTestBindDataTypes
+     */
+    public function testBindDataTypes($data, $expectedException)
+    {
+        // arrange
+        $query = 'SELECT * FROM test WHERE id = ?';
+        $stmtId = 1;
+        $paramId = 0;
+        $named = [];
+
+        $this->processor->alive()->willReturn(true);
+        $this->processor->delRef()->shouldBeCalled();
+        $this->processor->closeStmt(\Prophecy\Argument::any())->shouldBeCalled();
+        $this->resultProxy->columnsToFetch = 1;
+        $stmt = new Stmt($this->processor->reveal(), $query, $stmtId, $named, $this->resultProxy);
+
+        // assert
+        if ($expectedException) {
+            $this->expectException($expectedException);
+            $this->processor->bindParam($stmtId, \Prophecy\Argument::any(), $data)->shouldNotBeCalled();
+        } else {
+            $this->addToAssertionCount(1);
+            $this->processor->bindParam($stmtId, \Prophecy\Argument::any(), $data)->shouldBeCalled();
+        }
+
+        // act
+        $stmt->bind($paramId, $data);
+    }
+
+    public function provideTestBindDataTypes()
+    {
+        return [
+            'test scalar' => [
+                'data' => 1,
+                'expectedException' => false,
+            ],
+            'test object' => [
+                'data' => (object) [],
+                'expectedException' => 'InvalidArgumentException',
+            ],
+            'test array' => [
+                'data' => [],
+                'expectedException' => 'InvalidArgumentException',
+            ],
+            'test object with __toString defined' => [
+                'data' => new class { public function __toString() {return '';} },
+                'expectedException' => false,
+            ],
+        ];
+    }
+}