$re = '/[\\\\]/';
$str = '<li class=\\"product-col\\"><div class=\\"product-inner\\"><div class=\\"product-image\\"><a href=\\"https:\\/\\/test.com\\/\\"><img width=\\"300\\" height=\\"300\\" src=\\"https:\\/\\/test.com\\/imgs\\/uploads\\/00894771000341_front-300x300.jpg\\" class=\\"img-fluid\\" alt=\\"\\"></a></div>Test Product</div></li>';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php