Description
Used to perform custom validation on an attachment and prevent it being uploaded or selected for a specific field.
Similar to the acf/upload_prefilter filter, this filter can be used to prevent an upload, however, it can also be used to prevent an attachment being selected from a WP media modal.
Changelog
- Added in version 5.2.8
- Added
contextparameter in version 5.6.3
Parameters
apply_filters( 'acf/validate_attachment', $errors, $file, $attachment, $field, $context );$errors(array) An array of error messages (strings) for the given attachment. Appending to this array will result in the attachment failing to upload, and the error message displayed to the client.$file(array) An array of generic file data including type, width, height and size$attachment(array) The attachment being uploaded/displayed. This data changes depending on context$field(array) The field array containing all settings.$context(string) Description of the current context: upload, basic_upload (when uploading) or prepare (when viewing). Added in 5.6.3
Modifers
This filter provides modifiers to target specific fields. The following filter names are available:
acf/validate_attachmentApplies to all fields.acf/validate_attachment/type={$type}Applies to all fields of a specific type.acf/validate_attachment/name={$name}Applies to all fields of a specific name.acf/validate_attachment/key={$key}Applies to all fields of a specific key.
Example
This example demonstrates how to validate the file name of all attachments. If the attachmentâs file name does not begin with the string "acf-", an error message will be displayed causing the upload/selection to fail.
functions.php
<?php
add_filter('acf/validate_attachment', 'my_acf_validate_attachment', 10, 5);
function my_acf_validate_attachment( $errors, $file, $attachment, $field, $context ){
// Check first 4 characters of the attachment name.
if( substr($attachment['name'], 0, 4) !== 'acf-' ) {
$errors[] = __( 'File name must begin with "acf-"' );
}
return $errors;
}