具体实现方法如下：

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;
}