我在这里收到一些PHP代码:
<?PHP echo 'hello ' . 1 + 2 . '34'; ?>
其输出234,
但是当我在“hello”之前添加一个数字11:
<?PHP echo '11hello ' . 1 + 2 . '34'; ?>
它输出1334而不是245(我预计它),为什么呢?
真奇怪…
但
<?PHP echo '11hello ' . (1 + 2) . '34'; ?>
要么
<?PHP echo '11hello ',1 + 2,'34'; ?>
修复问题.
UPDv1:
最后设法得到正确答案:
‘hello’= 0(不包含前导数字,所以PHP假定它为零).
所以你好. 1 2简化为’hello1’2是2,因为’hello1’中的前导数字也不为零.
’11hello’= 11(包含前导数字,所以PHP假定是十一).
所以’11hello’. 1 2简化为“11和1”2,因为11 2是13.
UPDv2:
http://www.php.net/manual/en/language.types.string.php
The value is given by the initial portion of the string. If the string starts with valid numeric data,this will be the value used. Otherwise,the value will be 0 (zero). Valid numeric data is an optional sign,followed by one or more digits (optionally containing a decimal point),followed by an optional exponent. The exponent is an ‘e’ or ‘E’ followed by one or more digits.