Wordpress在PHP升级后出现非法字符串偏移警告

Question

将wordpress安装从开发移动到实时主机后，非法字符串偏移警告已开始出现。违规代码与下面显示的自定义表单插件功能有关：

function __construct( $data='', $args='' ) {
    if( is_array($args) ) extract($args);

    // Show start & end tags
    $this->formtags = true;

    // Echo the form
    $this->echo = true;

    // Use Ajax
    $this->ajax = true;

    // Show ":" in labels
    if( !$colon ) $this->colon = $colon;
    else $this->colon = true;

    // Process as collection of "p" elements
    $this->class_mode = 'p'; // 'p', 'input'

    // Set path for our transformations
    $this->path = $path ? $path : dirname(__FILE__);

    // Sanitize & assign data & xsl
    if( !$data ) $data = 'contact';
    $this->set( $data );

    //Set Wrapper tag
    if( $args['wrapper_tag'] ) $this->wrapper_tag = $args['wrapper_tag'];
    else $this->wrapper_tag = 'p';
}

最终的if / else语句导致问题：

if( $args['wrapper_tag'] ) $this->wrapper_tag = $args['wrapper_tag'];
        else $this->wrapper_tag = 'p';