Returns a specified column in an array

Extract the same key and the value corresponding to the key from the two-dimensional array to form a new array,
PHP5.5 has been released, which adds a new array function array_column, which feels good! However, if you want to use a lower version of PHP, you have to implement it yourself, so the lower version of PHP does not support this function, so I found it in PHP and wrote it under the function of tp
//array_column — Returns a column specified in the arrayfunction arrayColumn( array $array, $column_key, $index_key=null){<br> //This function is used to check whether the specified function has been defined. The parameter function_name is the name of the function to be checked. If the specified function has been defined, it returns a true value, otherwise it returns a false value. <br> If(function_exists('array_column')){<br>                  return array_column($array, $column_key, $index_key);<br>          }<br>          $result = array();<br> foreach($array as $arr){<br>                   if(!is_array($arr)) continue;<br> <br> If(is_null($column_key)){<br>                 $value = $arr;<br>                  }else{<br>                   $value = $arr[$column_key];<br>             }<br> <br> If(!is_null($index_key)){<br>                  $key = $arr[$index_key];<br>                   $result[$key] = $value;<br>                  }else{<br>                   $result[] = $value;<br>             }<br> <br>          }<br> <br> Return $ result; <br> }