Validate WYSIWYG character limit

validate-acf-wysiwyg.php

<?php

/**
 * Validate WYSIWYG field so that it outputs only 250 characters
 *
 * Targets the overview field in the documentation only.
 *
 * @param  bool   $valid Check the validity of the field.
 * @param  string $value The field value.
 * @param  array  $field Array with the field details.
 * @param  string $input Input string definition: acf[field_xxxxxxxxxxxxx].
 * @return bool|string   True if valid, fail if invalid.
 */
public function validate_wysiwyg_field_length( bool $valid, string $value, array $field, string $input ) {
  if ( ! $valid ) {
    return $valid;
  }

  if ( strlen( wp_strip_all_tags( $value ) ) > 250 ) {
      $valid = esc_html__( 'Maximum limit for the input is 250 characters.', 'developer-portal' );
  }
  return $valid;
}