$source_content = preg_replace($search, "'"
                                       . $this->_quote_replace($this->left_delimiter) . 'php'
                                       . "' . str_repeat(\"\n\", substr_count('\\0', \"\n\")) .'"
                                       . $this->_quote_replace($this->right_delimiter)
                                       . "'"
                                       , $source_content);

replacement 输出为
string '<{php' . str_repeat("
", substr_count('0', "
")) .'}>' (length=54)