<?php
function array_to_json( $array ){

      if( !is_array( $array ) ){
          return false;
      }

      $associative = count( array_diff( array_keys($array), array_keys( array_keys( $array )) ));
      if( $associative ){

          $construct = array();
          foreach( $array as $key => $value ){

              // We first copy each key/value pair into a staging array,
              // formatting each key and value properly as we go.

              // Format the key:
              if( is_numeric($key) ){
                  $key = "key_$key";
              }
              $key = "\"".addslashes($key)."\"";

              // Format the value:
              if( is_array( $value )){
                  $value = array_to_json( $value );
              } else if( !is_numeric( $value ) || is_string( $value ) ){
                  $value = "\"".addslashes($value)."\"";
              }

              // Add to staging array:
              $construct[] = "$key: $value";
          }

          // Then we collapse the staging array into the JSON form:
          $result = "{ " . implode( ", ", $construct ) . " }";

      } else { // If the array is a vector (not associative):

          $construct = array();
          foreach( $array as $value ){

              // Format the value:
              if( is_array( $value )){
                  $value = array_to_json( $value );
              } else if( !is_numeric( $value ) || is_string( $value ) ){
                  $value = "'".addslashes($value)."'";
              }

              // Add to staging array:
              $construct[] = $value;
          }

          // Then we collapse the staging array into the JSON form:
          $result = "[ " . implode( ", ", $construct ) . " ]";
      }

      return $result;
  }
?>