doublesharp

<h4>Validated Field Add-On</h4>
The Validated Field add-on for <a href="https://wordpress.org/extend/plugins/advanced-custom-fields/" rel="ugc">Advanced Custom Fields</a> 
provides a wrapper for other input types which allows you to provide client side input masking using the jQuery 
<a href="http://digitalbush.com/projects/masked-input-plugin/" rel="nofollow ugc">Masked Input Plugin</a>, server side validation using either PHP regular expressions 
or PHP code, the option of ensuring a field’s uniqueness for all posts by <code>post_type</code> and <code>meta_key</code>, <code>post_type</code>, or site wide, or a 
single post by meta_key, as well as marking a field as read-only. Edit your fields in the ACF Field Group editor and update code using the ACE.js 
IDE with autocomplete and syntax validation.
<h4>Features</h4>
<ol>
<li>Input Masking – easily set masks on text inputs to ensure data is properly formatted.</li>
<li>Server-Side Validation – validate the inputs using server side PHP code or regular expressions.</li>
<li>Uniqueness – ensure that the value being updated is not already in use.</li>
<li>Repeater Fields – validated fields within a <a href="http://www.advancedcustomfields.com/add-ons/repeater-field/" rel="nofollow ugc">Repeater Field</a>.</li>
<li>Read Only – specify a field as read-only allowing it to be displayed but not updated.</li>
<li>WordPress Multi Language – compatible with multilingual sites using the WPML plugin.</li>
<li>Conditional Logic – show and hide validated fields based on the values of other “switch” fields.</li>
</ol>
<h4>Compatibility</h4>
Requires <a href="https://wordpress.org/extend/plugins/advanced-custom-fields/" rel="ugc">Advanced Custom Fields</a> version 4.0 or greater.

Advanced Custom Fields: Validated Field

Adding my one star to inform people that this plugin is no longer working

Doesn't work in ACF Pro 5.6.2

The Validated Field add-on for Advanced Custom Fields provides input masking and server-side validation of other field types.

Arefly

Check if the Email’s Gravatar is exist.
檢測指定郵箱的Gravatar是否存在
Example:
<pre><code>if(validate_gravatar("name@domain.com")){
 echo "This Email have Gravatar!";
}else{
 echo "This Email do not have Gravatar!";
}
</code></pre>

Validate Gravatar

Check if the Email's Gravatar is exist. 檢測指定郵箱的Gravatar是否存在

Advanced Custom Fields: Validated Field vs Validate Gravatar