PHP customized array_column function for recursion, named array_column_recursive

array_column_recursive.php

<?php
if ( ! function_exists( 'array_column_recursive' ) ) {
	/**
	 * Returns the values recursively from columns of the input array, identified by
	 * the $columnKey.
	 *
	 * Optionally, you may provide an $indexKey to index the values in the returned
	 * array by the values from the $indexKey column in the input array.
	 *
	 * @param array $input     A multi-dimensional array (record set) from which to pull
	 *                         a column of values.
	 * @param mixed $columnKey The column of values to return. This value may be the
	 *                         integer key of the column you wish to retrieve, or it
	 *                         may be the string key name for an associative array.
	 * @param mixed $indexKey  (Optional.) The column to use as the index/keys for
	 *                         the returned array. This value may be the integer key
	 *                         of the column, or it may be the string key name.
	 *
	 * @return array
	 */
	function array_column_recursive( $input = NULL, $columnKey = NULL, $indexKey = NULL ) {

		// Using func_get_args() in order to check for proper number of
		// parameters and trigger errors exactly as the built-in array_column()
		// does in PHP 5.5.
		$argc   = func_num_args();
		$params = func_get_args();
		if ( $argc < 2 ) {
			trigger_error( "array_column_recursive() expects at least 2 parameters, {$argc} given", E_USER_WARNING );

			return NULL;
		}
		if ( ! is_array( $params[ 0 ] ) ) {
			// Because we call back to this function, check if call was made by self to
			// prevent debug/error output for recursiveness :)
			$callers = debug_backtrace();
			if ( $callers[ 1 ][ 'function' ] != 'array_column_recursive' ){
				trigger_error( 'array_column_recursive() expects parameter 1 to be array, ' . gettype( $params[ 0 ] ) . ' given', E_USER_WARNING );
			}

			return NULL;
		}
		if ( ! is_int( $params[ 1 ] )
		     && ! is_float( $params[ 1 ] )
		     && ! is_string( $params[ 1 ] )
		     && $params[ 1 ] !== NULL
		     && ! ( is_object( $params[ 1 ] ) && method_exists( $params[ 1 ], '__toString' ) )
		) {
			trigger_error( 'array_column_recursive(): The column key should be either a string or an integer', E_USER_WARNING );

			return FALSE;
		}
		if ( isset( $params[ 2 ] )
		     && ! is_int( $params[ 2 ] )
		     && ! is_float( $params[ 2 ] )
		     && ! is_string( $params[ 2 ] )
		     && ! ( is_object( $params[ 2 ] ) && method_exists( $params[ 2 ], '__toString' ) )
		) {
			trigger_error( 'array_column_recursive(): The index key should be either a string or an integer', E_USER_WARNING );

			return FALSE;
		}
		$paramsInput     = $params[ 0 ];
		$paramsColumnKey = ( $params[ 1 ] !== NULL ) ? (string) $params[ 1 ] : NULL;
		$paramsIndexKey  = NULL;
		if ( isset( $params[ 2 ] ) ) {
			if ( is_float( $params[ 2 ] ) || is_int( $params[ 2 ] ) ) {
				$paramsIndexKey = (int) $params[ 2 ];
			} else {
				$paramsIndexKey = (string) $params[ 2 ];
			}
		}
		$resultArray = array();
		foreach ( $paramsInput as $row ) {
			$key    = $value = NULL;
			$keySet = $valueSet = FALSE;
			if ( $paramsIndexKey !== NULL && is_array( $row ) && array_key_exists( $paramsIndexKey, $row ) ) {
				$keySet = TRUE;
				$key    = (string) $row[ $paramsIndexKey ];
			}
			if ( $paramsColumnKey === NULL ) {
				$valueSet = TRUE;
				$value    = $row;
			} elseif ( is_array( $row ) && array_key_exists( $paramsColumnKey, $row ) ) {
				$valueSet = TRUE;
				$value    = $row[ $paramsColumnKey ];
			}

			$possibleValue = array_column_recursive( $row, $paramsColumnKey, $paramsIndexKey );
			if ( $possibleValue ) {
				$resultArray = array_merge( $possibleValue, $resultArray );
			}

			if ( $valueSet ) {
				if ( $keySet ) {
					$resultArray[ $key ] = $value;
				} else {
					$resultArray[ ] = $value;
				}
			}
		}

		return $resultArray;
	}
}

There is a bug at line 76 which sometimes causes a warning that $row is not an array (array_key_exists requires an array as argument 2). The solution is to add if(is_array($row)) { before line 76 (and the closing bracket at line 80 obviously...).

As a side note - I referenced this Gist here ramsey/array_column#6 (comment) as a reference for implementing a recursive column function as part of the pre-5.5 array_column library and as an enhancement for PHP Core.

@ckmaresca thanks I updated it adding the is_array( $row ) check in that if statement

Thanks for this function! Much better than the array_walk_recursive one that seems to be suggested in other places (which doesn't factor in an array as the result of the column you're looking for).

Have had to make one modification where the recursive call was triggering an error when $row wasn't an array:

			if (is_array( $row )) {
				$possibleValue = array_column_recursive( $row, $paramsColumnKey, $paramsIndexKey );
				if ( $possibleValue ) {
					$resultArray = array_merge( $possibleValue, $resultArray );
				}
			}