说PHP入门门槛低，其中一个原因是我们不需要关心变量的类型，PHP为我们做了自动的转化。但事实上是这样吗？下面就是一个隐蔽的bug。
字符串 == 比较类型强转隐患
http://php.net/manual/zh/language.operators.comparison.php
// php 5
var_dump(md5('240610708') == md5('QNKCDZO'));//bool(true)
var_dump(md5('aabg7XSs') == md5('aabC9RqS'));//bool(true)
var_dump(sha1('aaroZmOk') == sha1('aaK1STfY'));//bool(true)
var_dump(sha1('aaO8zKZF') == sha1('aa3OFF9m'));//bool(true)
var_dump('0010e2' == '1e3');//10×10^2 = 1×10^3 bool(true)
var_dump('0x1234Ab' == '1193131');//bool(true)
var_dump('0xABCdef' == ' 0xABCdef');//bool(true)
var_dump('0e1' == '0e2'); //bool(true)
// php 7 含十六进制字符串不再被认为是数字 http://php.net/manual/zh/migration70.incompatible.php
var_dump('0x1234Ab' == '1193131');//bool(false)
var_dump('0xABCdef' == ' 0xABCdef');//bool(false)
var_dump("0x123" == "291");//bool(false)
var_dump(is_numeric("0x123"));//bool(false)
>>> md5('240610708')
=> "0e462097431906509019562988736854"
>>> md5('QNKCDZO')
=> "0e830400451993494058024219903391"
// php 是弱语言，会自动判断数据类型,0eXXXXXXXXXX 转成 0 了
//来自文档：如果比较一个数字和字符串或者比较涉及到数字内容的字符串，则字符串会被转换为数值并且比较按照数值来进行。此规则也适用于 switch 语句。当用 === 或 !== 进行比较时则不进行类型转换，因为此时类型和数值都要比对。
>>> md5('QNKCDZO')==0
=> true
>>> md5('240610708')==0
=> true
// 使用 === 判断 官方都建议直接用password_hash加密
var_dump(md5('240610708') === md5('QNKCDZO'));//bool(false)
ps: php 7 优化和不兼容
PDO bindParam 要求第二个参数是一个引用变量
http://www.laruence.com/2012/10/16/2831.html
$dbh = new PDO('mysql:host=localhost;dbname=test', "test");
$query = <<<QUERY
INSERT INTO `user` (`username`, `password`) VALUES (:username, :password);
QUERY;
$statement = $dbh->prepare($query);
$bind_params = array(':username' => "laruence", ':password' => "weibo");
foreach( $bind_params as $key => $value ){
$statement->bindParam($key, $value);
}
$statement->execute();
//期望执行 sql
INSERT INTO `user` (`username`, `password`) VALUES ("laruence", "weibo");
// 实际执行 sql
INSERT INTO `user` (`username`, `password`) VALUES ("weibo", "weibo");
//第一次循环
$value = $bind_params[":username"];
$statement->bindParam(":username", &$value); //此时, :username是对$value变量的引用
//第二次循环
$value = $bind_params[":password"]; //oops! $value被覆盖成了:password的值
$statement->bindParam(":password", &$value);
// 解决
foreach( $bind_params as $key => &$value ) { //注意这里
$statement->bindParam($key, $value);
}
return $statement->execute($params);
PHP 引用
https://glot.io/snippets/estgofa359
参考鸟哥一条微博
-
$arr
= range
(1
,3
);
-
foreach
($arr as
&$v
){
-
-
}
-
foreach
($arr as $v
){
-
-
}
-
print_r
($arr
);//[1,2,2]
-
-
// 解决一
-
$arr
= range
(1
,3
);
-
foreach
($arr as
&$v
){
-
-
}
-
unset
($v
);
-
foreach
($arr as $v
){
-
-
}
-
print_r
($arr
);//[1,2,3]
-
// 解决二
-
$arr
= range
(1
,3
);
-
foreach
($arr as
&$v
){
-
-
}
-
foreach
($arr as $v2
){
-
-
}
-
print_r
($arr
);//[1,2,3]
-
// 解决三
-
$arr
= range
(1
,3
);
-
foreach
($arr as
&$v
){
-
-
}
-
foreach
($arr as
&$v
){
-
-
}
-
print_r
($arr
);//[1,2,3]
array_merge vs +
https://glot.io/snippets/estgpi43bc
//
$arr1 = array(1 => "one", "2" => "two", 3 => "three");
$arr2 = array(2 => "new two", 3 => "new three");
print_r($arr1 + $arr2);
Array
(
[1] => one
[2] => two
[3] => three
)
print_r(array_merge($arr1, $arr2));
Array
(
[0] => one
[1] => two
[2] => three
[3] => new two
[4] => new three
)
浮点数精度问题
http://php.net/manual/zh/language.types.float.php
var_dump(15702>=(157.02*100));//bool(false)
var_dump(11111>=(111.11*100));//bool(true)
var_dump(bcsub(15702,(157.02*100)) >= 0);//bool(true)
if(abs(15702-(157.02*100)) < 0.001) {
echo "相等";
} else {
echo "不相等";
}
$f = 0.58;
var_dump(intval($f * 100)); //57 0.58 * 100 = 57.999999999...
in_array switch
https://glot.io/snippets/esth249n0y
$arr = ['a', 'pro' => 'php', 8, true];
var_dump(in_array(2, $arr)); // bool(true)
var_dump(in_array('b', $arr)); // bool(true)
var_dump(in_array(0, $arr)); // tbool(true)
var_dump(in_array(null, $arr)); // bool(false)
var_dump(in_array(2, $arr, true)); // bool(false)
var_dump(in_array(0, $arr, true)); // bool(false)
$name = 0;
switch ($name) {
case "a":
//...
break;
case "b":
//...
break;
}
switch (strval($name)) {
case "a":
//...
break;
case "b":
//...
break;
}
strpos
https://glot.io/snippets/esthlvjtki
function getReferer($link)
{
$refMap = [
'baidu' => '百度',
'sougou' => '搜狗',
'360' => '360',
'google' => '谷歌'
];
foreach ($refMap as $key => $value) {
if (strpos($link, $key) !== false) {
return $value;
}
}
return '其他';
}
// https://secure.php.net/manual/zh/function.strpos.php 如果 needle 不是一个字符串，那么它将被转换为整型并被视为字符的顺序值。
echo getReferer('https://www.google.com/search?workd=google');//360
// 解决
function getReferer($link)
{
$refMap = [
'baidu' => '百度',
'sougou' => '搜狗',
'360' => '360',
'google' => '谷歌'
];
foreach ($refMap as $key => $value) {
if (mb_strpos($link, $key) !== false) {
//if (strpos($link, strval($key)) !== false) {
return $value;
}
}
return '其他';
}
curl 文件上传
http://php.net/manual/zh/curlfile.construct.php
//PHP的cURL支持通过给CURL_POSTFIELDS传递关联数组（而不是字符串）来生成multipart/form-data的POST请求
if (class_exists('\CURLFile')) {
$field = array('fieldname' => new \CURLFile(realpath($filepath)));
} else {
$field = array('fieldname' => '@' . realpath($filepath));
}
foreach 顺序
$arr=[];
$arr[2] = 2;
$arr[1] = 1;
$arr[0] = 0;
foreach ($arr as $key => $val) {
echo $val;// 2 1 0
}
while (list($key, $v) = each($arr)) {
//获取不到 foreach会自动reset，each之前, 先reset数组的内部指针
}
for($i=0,$l=count($arr); $i<$l; $i++) {
echo $arr[$i];// 0 1 2
}
json_decode
>>> json_decode('php')
=> null
>>> json_decode('0x123')
=> 291
strtotime('-x month')
date_default_timezone_set('Asia/Shanghai');
$t = strtotime('2017-08-31');
echo date('Ym',strtotime('- 1 month',$t));//201707
echo date('Ym',strtotime('- 2 month',$t));//201707
//
$first_day_of_month = date('Y-m',strtotime('2017-08-31')) . '-01 00:00:01';
$t = strtotime($first_day_of_month);
echo date('Ym',strtotime('- 1 month',$t));//201707
echo date('Ym',strtotime('- 2 month',$t));//201706
echo date("Ym", strtotime("-2 month", strtotime("first day of 2017-08-31")));//201706
