Worpress Contact Form 7 - Textarea Validation - Your Message

wpcf7_validate_textarea.php

add_filter( 'wpcf7_validate_textarea', 'no_urls_allowed', 10, 3 );
add_filter( 'wpcf7_validate_textarea*', 'no_urls_allowed', 10, 3 );

function no_urls_allowed( $result, $tag ) {

    $tag = new WPCF7_Shortcode( $tag );

    $type = $tag->type;
    $name = $tag->name;

    $value = isset( $_POST[$name] )
        ? trim( wp_unslash( strtr( (string) $_POST[$name], "\n", " " ) ) )
        : '';

    // If this is meant to be a URL field, do nothing
    if ( 'url' == $tag->basetype || stristr($name, 'url') ) {
        return $result;
    }

    // Check for URLs
    $value = $_POST[$name];
    $not_allowed = array( 'http://', 'https://', 'www.', '[url', '<a ', ' seo ' );
    foreach ( $not_allowed as $na ) {
        if ( stristr( $value, $na ) ) {
            $result->invalidate( $tag, 'URLs are not allowed' );
            return $result;
        }
    }
    return $result;
}