Adds a callback for Dynamic Field "Get value from repeater field". It allows getting the value from the specified sub-field and row number of the repeater on the single post page and in listings.

jec_repeater_callback.php

add_action( 'jet-engine/callbacks/register', function( $callbacks ) {

	$args = array(
		'repeater_name' => array(
			'label'   => 'Repeater Field key',
			'type'    => 'text',
		),
		'sub_field_name' => array(
			'label' => 'Sub-field name',
			'type'    => 'text',
			),
		'row_number' => array(
			'label' => 'Row number starting from 0',
			'type' => 'text',
		),
	);
	
	$callbacks->register_callback( 'jec_repeater_callback', 'Get value from repeater field', $args );

	function jec_repeater_callback( $value, $rep_name, $sub_field_name, $row ) {
		
		if ( empty( $value ) ) {
		return;
		}

		$result = '';

		if ( empty( $rep_name ) || empty( $sub_field_name ) ) {
			return '';
		}

		$index = 0;

		if ( is_numeric( $row ) ) {

			if ( str_starts_with( $row, '+' ) ) {
				$coff  = trim( $row, '+' );
				$row = $index + + $coff;
			}

			if ( str_starts_with( $row, '-' ) ) {
				$coff  = trim( $row, '-' );
				$row = $index - + $coff;
			}

			} else {
			
			$row = $index;
			
		}

		$fields = get_post_meta( $value, $rep_name, true );
		$row    = $fields[ 'item-' . $row ] ?? array();

		return $row[ $sub_field_name ] ?? '';
		
	}

} );