一個函數對於標量參數可以定義C++-風格的默認值.
function makecoffee ($type = "cappucino") {
echo "Making a cup of $type.
";
}
echo makecoffee ();
echo makecoffee ("espresso");
上面的程序段的輸出如下:
Making a cup of cappucino.
Making a cup of espresso.
默認值必須是一個常量表達式,不是一個變量或類成員.
注意當時用默認參數時,任何默認都應該在任何非默認參數右邊;否則,事情將不會想你所想的那樣.考慮下面的程序段:
function makeyogurt ($type = "acidophilus", $flavour) {
return "Making a bowl of $type $flavour.
";
}
echo makeyogurt ("raspberry"); // 將不會按照預想工作
上面例子的輸出是:
Warning: Missing argument 2 in call to makeyogurt() in
/usr/local/etc/httpd/htdocs/php3test/functest.html on line 41
Making a bowl of raspberry .
現在,用下面的對比上面的:
function makeyogurt ($flavour, $type = "acidophilus"){
return "Making a bowl of $type $flavour.
";
}
echo makeyogurt (“raspberry”);//正常工作
這個例子的輸出是:
Making a bowl of acidophilus raspberry.
