The Meta Tag Checker.

A customisable validator for web page meta tags, including Facebook open graph tags and Twitter card tags. Having correct meta tags can improve SEO and clickthroughs on social networks.

Live demo here.

Features

• Check tags exist and have valid contents.
• Results can be accessed programmatically via API.
• Easy to customise which tags are checked and their validation rules.

Getting started

1. Download this repository.
2. composer install (If you don't have Composer installed, installation instructions are here.
3. Upload to your web host, in any directory.
4. Optional: Customise the JSON schema (see below for further instructions).

Results API

In addition to the main results page, you can get a JSON representation of the results by adding /api/ to the URL.

Customising the validator schema

The meta tags and their rules are specified in config/schema.json.

Key	Example value	Description
selector	link[rel='image_src']	CSS selector for meta tag.
attribute	href	(optional) Tag property to get content from. Defaults to inner text.
pattern	/(^http:\/\/)/	Regex (regular expression) which validates content of tag. Returns 'ok' if it finds a match. Make sure to escape slashes (so it's valid JSON) and leave out the global 'g'.
hint	URL of a promo image.	Human-readable description of the pattern.
group	meta	(optional) Used to sort tags into groups.
longname	Teaser image	Descriptive name for humans.
type	image	(optional) Set to 'image' if result should be a JPG/PNG/GIF. Other options: 'url', 'strict-url' (see below for more details).
url	https://dev.twitter.com/cards/types	(optional) URL with further information about meta tag.

Example regex rules

If you're customising the schema, you'll need to write your rules using regular expressions (regexes). The meta tags's contents are considered 'ok' if the regex finds a match.

Below are a few examples to get you started. For writing your own rules, Regexr is a useful resource.

Regex	Escaped regex	Description
/./	\/.\/	Matches non-blank values.
/[^(replace this)]/	\/[^(replace this)]\/	Matches values which do not contain replace this.
/(^http)/	\/(^http)\/	Matches values beginning with http.
/(^http).*(_NS_)[^\s]*/	\/(^http).*(_NS_)[^\\s]*\/	Matches values beginning with http and containing the string _NS_.

Custom selectors

Need to find something in the document by something other than a CSS selector? Simply add a new function to the $custom_functions array in custom.php. You can specify it using a selector custom:yourFunctionName.

Custom validators

Need to validate a value with something more complex than a regular experession? As with custom validators, simply add a new function to the $custom_functions array in $custom.php. You can specify it using a validator custom:yourFunctionName.

Example custom validator

This function checks that an image is square.

$custom_functions = Array(
    'squareImage' => function($image_url) {
        // use PHP's builtin getimagesize function to get height and width of image
        $size = getimagesize( $image_url);
        $w = $size[0];
        $h = $size[1];
        // divide to get ratio
        $ratio = $w/$h;
        // return false if not square
        if ($ratio !== 1) {
            return false;
        }
        return true;
    },
    // ... more functions here ...
);

Then in schema.json, specify the function's name in the pattern field of your item:

{
    "selector": "link[rel='image_src']",
    "attribute": "href",
    "longname": "Promo image",
    "type": "image",
    "pattern": "custom:squareImage",
    "hint": "Should be a URL of a square image."
}

Content types

• 'image': Renders content on frontend in tag.
• 'url': Checks header of URL to make sure link is valid, and renders in tag.
• 'strict-url': Same as 'url', but rejects redirect headers (eg. 301s). Useful for canonical URLs.

Running behind a proxy

Add a file called proxy.php to the config directory. Within the file, use stream_context_set_default to configure the proxy.

Changelog

2.0.1

• Shorter timeout when checking URL validity

2.0.0

• Simplified proxy configuration

1.0.1

• New content types: 'url' and 'strict-url'

1.0.0

• Initial release