php中正则替换函数ereg_replace用法实例

$num = '49';
$string = "this string has four words";
$string = ereg_replace ('four', $num, $string);
echo $string;

$string ="测试用文字";
echo "$string<p>";
$string = ereg_replace ("^", "<br>", $string);
$string = ereg_replace ("$", "<br>", $string);
echo "==========$string==========";