Regex validation rules

functions.php

<?php

add_filter('submit_job_form_validate_fields', function( $isValid, $fields, $values ) {

    foreach ( $fields['job'] as $key => $field ) {
	
	// Example regex validation
        if ( $field['slug'] == 'phone' && isset( $values['job']['phone'] ) && preg_match( "/(foo)(bar)/", $values['job']['phone'] ) ) {
            return new \WP_Error( 'validation-error', sprintf( __( '%s isn\'t valid', 'my-listing' ), $field['label'] ) );
        }
    }

    return $isValid;
}, 100, 3);