php中字符串和数字比较时自动转换类型的问题

最新推荐文章于 2020-03-25 22:52:27 发布

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本文解析了PHP中字符串与数字进行比较时的转化规则。当字符串与整数进行比较时，字符串会被转换为数字；若两个数值型字符串比较，则按整数比较。文章通过实例展示了这些规则，并解释了switch语句中的应用。

字符串会被转化为0，请看以下说明：

If you compare an integer with a string, the string is converted to a number. If you compare two numerical strings, they are compared as integers. These rules also apply to the switch statement.

<?php
var_dump(0 == "a"); // 0 == 0 -> true
var_dump("1" == "01"); // 1 == 1 -> true
var_dump("1" == "1e0"); // 1 == 1 -> true

switch ("a") {
case 0:
    echo "0";
    break;
case "a": // never reached because "a" is already matched with 0
    echo "a";
    break;
}
?>

参见[url]http://cn2.php.net/manual/en/language.operators.comparison.php[/url]