这是什么?

这是一些关于在编程PHP时可能遇到的警告、错误和注意事项的答案,而不知道如何修复它们。这也是一个社区维基,所以每个人都被邀请加入和维护这个列表。

为什么会这样?

Questions like "Headers already sent" or "Calling a member of a non-object" pop up frequently on Stack Overflow. The root cause of those questions is always the same. So the answers to those questions typically repeat them and then show the OP which line to change in their particular case. These answers do not add any value to the site because they only apply to the OP's particular code. Other users having the same error cannot easily read the solution out of it because they are too localized. That is sad because once you understood the root cause, fixing the error is trivial. Hence, this list tries to explain the solution in a general way to apply.

我该怎么做呢?

如果您的问题被标记为此问题的副本,请在下面找到您的错误消息并将修复应用于您的代码。答案通常包含进一步的调查链接,以防仅从一般答案中不清楚。

如果您想投稿,请添加您“最喜欢的”错误消息、警告或通知,每个答案一条,简短描述它的含义(即使它只是突出显示手册页的术语),可能的解决方案或调试方法,以及现有的有价值的问答列表。此外,请随意改进任何现有的答案。

列表

Nothing is seen. The page is empty and white. (also known as White Page/Screen Of Death) Code doesn't run/what looks like parts of my PHP code are output Warning: Cannot modify header information - headers already sent Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given a.k.a. Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource Warning: [function] expects parameter 1 to be resource, boolean given Warning: [function]: failed to open stream: [reason] Warning: open_basedir restriction in effect Warning: Division by zero Warning: Illegal string offset 'XXX' Warning: count(): Parameter must be an array or an object that implements Countable Parse error: syntax error, unexpected '[' Parse error: syntax error, unexpected T_XXX Parse error: syntax error, unexpected T_ENCAPSED_AND_WHITESPACE Parse error: syntax error, unexpected T_PAAMAYIM_NEKUDOTAYIM Parse error: syntax error, unexpected 'require_once' (T_REQUIRE_ONCE), expecting function (T_FUNCTION) Parse error: syntax error, unexpected T_VARIABLE Fatal error: Allowed memory size of XXX bytes exhausted (tried to allocate XXX bytes) Fatal error: Maximum execution time of XX seconds exceeded Fatal error: Call to a member function ... on a non-object or null Fatal Error: Call to Undefined function XXX Fatal Error: Cannot redeclare XXX Fatal error: Can't use function return value in write context Fatal error: Declaration of AAA::BBB() must be compatible with that of CCC::BBB()' Return type of AAA::BBB() should either be compatible with CCC::BBB(), or the #[\ReturnTypeWillChange] attribute should be used Fatal error: Using $this when not in object context Fatal error: Object of class Closure could not be converted to string Fatal error: Undefined class constant Fatal error: Uncaught TypeError: Argument #n must be of type x, y given Notice: Array to string conversion (< PHP 8.0) or Warning: Array to string conversion (>= PHP 8.0) Notice: Trying to get property of non-object error Notice: Undefined variable or property "Notice: Undefined Index", or "Warning: Undefined array key" Notice: Undefined offset XXX [Reference] Notice: Uninitialized string offset: XXX Notice: Use of undefined constant XXX - assumed 'XXX' / Error: Undefined constant XXX MySQL: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ... at line ... Strict Standards: Non-static method [<class>::<method>] should not be called statically Warning: function expects parameter X to be boolean/string/integer HTTP Error 500 - Internal server error Deprecated: Arrays and strings offset access syntax with curly braces is deprecated

还看到:

这个符号在PHP中是什么意思?


当前回答

解析错误:语法错误,意外的T_VARIABLE

可能的场景

我似乎找不到我的代码出了什么问题。以下是我的全部错误:

解析错误:语法错误,意外的T_VARIABLE在x行

我正在尝试的

$sql = 'SELECT * FROM dealer WHERE id="'$id.'"';

回答

解析错误:程序的语法问题,例如在语句的末尾遗漏了分号,或者像上面的情况一样,遗漏了。操作符。解释器在遇到解析错误时停止运行程序。

简单地说,这是一个语法错误,这意味着您的代码中有一些东西阻止了它被正确解析,从而无法运行。

您应该做的是仔细检查错误所在的行周围是否有任何简单的错误。

该错误消息意味着,在文件的第x行,PHP解释器期望看到一个开括号,但相反,它遇到了名为T_VARIABLE的东西。T_VARIABLE这个东西叫做令牌。它是PHP解释器表达程序不同基本部分的方式。当解释器读入程序时,它将您所编写的内容转换为令牌列表。无论你在程序中放入一个变量,解释器的列表中都会有一个aT_VARIABLE令牌。

不错的阅读:解析器令牌列表

因此,请确保在php.ini中至少启用了E_PARSE。产品脚本中不应该存在解析错误。

我总是建议在编码时添加以下语句:

error_reporting(E_ALL);

PHP错误报告

另外,使用IDE是个好主意,它可以让你在输入时知道解析错误。你可以使用:

NetBeans(一个漂亮的免费软件)(在我看来是最好的) PhpStorm(戈登叔叔喜欢这个:P,付费计划,包含专有和免费软件) Eclipse(美女与野兽,免费软件)

相关问题:

参考:PHP语法错误;以及如何解决这些问题?

其他回答

致命错误:当不在对象上下文时使用$this

$是PHP中的一个特殊变量,不能被赋值。如果在不存在该对象的上下文中访问该对象,则给出此致命错误。

此错误可能发生:

If a non-static method is called statically. Example: class Foo { protected $var; public function __construct($var) { $this->var = $var; } public static function bar () { // ^^^^^^ echo $this->var; // ^^^^^ } } Foo::bar(); How to fix: review your code again, $this can only be used in an object context, and should never be used in a static method. Also, a static method should not access the non-static property. Use self::$static_property to access the static property. If code from a class method has been copied over into a normal function or just the global scope and keeping the $this special variable. How to fix: Review the code and replace $this with a different substitution variable.

相关问题:

致命错误:当不在对象上下文中时使用$this 致命错误:当不在对象上下文中时使用$this 所有“使用$this时不在对象上下文”的问题在Stackoverflow

警告:function()期望参数X为布尔值(或整数,字符串等)

如果传递给函数的参数类型错误(PHP不能自动转换),就会抛出警告。此警告标识出哪个参数有问题,以及预期的数据类型。解决方案:将指定的参数更改为正确的数据类型。


例如下面的代码:

echo substr(["foo"], 23);

输出结果:

PHP警告:substr()期望参数1是字符串,数组给定

致命错误:超过XX秒的最大执行时间

每个PHP页面请求或脚本调用都度量PHP代码执行了多长时间。如果达到配置的限制,脚本将使用此消息中止。

注意,时间通常不包括发生在PHP“外部”的事情,例如等待数据库结果的时间,或使用shell_exec执行的外部程序等。例外情况是当PHP在Windows上运行时,测量的时间是“时钟时间”,并且确实包括这些外部等待时间。

常见的原因

无限循环。写错的while, do…while或for循环可能永远不会完成,这意味着PHP将永远持续运行。甚至foreach循环也可以是无限的,例如循环遍历一个Iterator对象或生成器函数。 庞大的数据集。即使您的循环不是无限的,如果它正在做很多工作,如果它正在处理大量的结果,它可能需要很长时间才能完成。

改变限制

如果你知道你有一个缓慢的过程,你可以配置时间限制:

在php.ini中,使用max_execution_time设置。 在脚本运行时,使用set_time_limit函数。注意,调用这个函数会将测量的时间重置为零,因此执行set_time_limit(10);意思是“再给10秒钟,不管脚本已经花了多长时间”。

这两种机制都应该给出一个秒数,或者特殊值0,表示“不限制”。设置“无限制”对于你真正想在后台永远运行的命令行脚本是最有用的;对于网页,最好设置一些有限值,即使它非常大,以防止代码中的错误导致整个系统失去响应。

严格标准:非静态方法[<class>::<method>]不应该被静态调用

当您试图在类上调用静态的非静态方法时发生,并且您在error_reporting()设置中也有E_STRICT标志。

例子:

class HTML {
   public function br() {
      echo '<br>';
   }
}

HTML::br()或$ HTML::br()

实际上,您可以通过不向error_reporting()添加E_STRICT来避免此错误,例如

error_reporting(E_ALL & ~E_STRICT);

因为对于PHP 5.4.0及以上版本,E_STRICT包含在E_ALL [ref]中。但这并不可取。解决方案是将你想要的静态函数定义为实际的静态函数:

public static function br() {
  echo '<br>';
}

或者按常规调用函数:

$html = new HTML();
$html->br();

相关问题:

我如何解决“非静态方法xxx:xxx()不应该在PHP 5.4中被静态调用?”

mysql_connect(): user 'name'@'host'拒绝访问

当您连接到无效或缺少凭据(用户名/密码)的MySQL/MariaDB服务器时,会出现此警告。所以这通常不是代码问题,而是服务器配置问题。

See the manual page on mysql_connect("localhost", "user", "pw") for examples. Check that you actually used a $username and $password. It's uncommon that you gain access using no password - which is what happened when the Warning: said (using password: NO). Only the local test server usually allows to connect with username root, no password, and the test database name. You can test if they're really correct using the command line client: mysql --user="username" --password="password" testdb Username and password are case-sensitive and whitespace is not ignored. If your password contains meta characters like $, escape them, or put the password in single quotes. Most shared hosting providers predeclare mysql accounts in relation to the unix user account (sometimes just prefixes or extra numeric suffixes). See the docs for a pattern or documentation, and CPanel or whatever interface for setting a password. See the MySQL manual on Adding user accounts using the command line. When connected as admin user you can issue a query like: CREATE USER 'username'@'localhost' IDENTIFIED BY 'newpassword'; Or use Adminer or WorkBench or any other graphical tool to create, check or correct account details. If you can't fix your credentials, then asking the internet to "please help" will have no effect. Only you and your hosting provider have permissions and sufficient access to diagnose and fix things. Verify that you could reach the database server, using the host name given by your provider: ping dbserver.hoster.example.net Check this from a SSH console directly on your webserver. Testing from your local development client to your shared hosting server is rarely meaningful. Often you just want the server name to be "localhost", which normally utilizes a local named socket when available. Othertimes you can try "127.0.0.1" as fallback. Should your MySQL/MariaDB server listen on a different port, then use "servername:3306". If that fails, then there's a perhaps a firewall issue. (Off-topic, not a programming question. No remote guess-helping possible.) When using constants like e.g. DB_USER or DB_PASSWORD, check that they're actually defined. If you get a "Warning: Access defined for 'DB_USER'@'host'" and a "Notice: use of undefined constant 'DB_PASS'", then that's your problem. Verify that your e.g. xy/db-config.php was actually included and whatelse. Check for correctly set GRANT permissions. It's not sufficient to have a username+password pair. Each MySQL/MariaDB account can have an attached set of permissions. Those can restrict which databases you are allowed to connect to, from which client/server the connection may originate from, and which queries are permitted. The "Access denied" warning thus may as well show up for mysql_query calls, if you don't have permissions to SELECT from a specific table, or INSERT/UPDATE, and more commonly DELETE anything. You can adapt account permissions when connected per command line client using the admin account with a query like: GRANT ALL ON yourdb.* TO 'username'@'localhost'; If the warning shows up first with Warning: mysql_query(): Access denied for user ''@'localhost' then you may have a php.ini-preconfigured account/password pair. Check that mysql.default_user= and mysql.default_password= have meaningful values. Oftentimes this is a provider-configuration. So contact their support for mismatches. Find the documentation of your shared hosting provider: e.g. HostGator, GoDaddy, 1and1, DigitalOcean, BlueHost, DreamHost, MediaTemple, ixWebhosting, lunarhosting, or just google yours´. Else consult your webhosting provider through their support channels. Note that you may also have depleted the available connection pool. You'll get access denied warnings for too many concurrent connections. (You have to investigate the setup. That's an off-topic server configuration issue, not a programming question.) Your libmysql client version may not be compatible with the database server. Normally MySQL and MariaDB servers can be reached with PHPs compiled in driver. If you have a custom setup, or an outdated PHP version, and a much newer database server, or significantly outdated one - then the version mismatch may prevent connections. (No, you have to investigate yourself. Nobody can guess your setup).

更多的引用:

mysql服务器错误:mysql用户无法访问root用户 mysql_connect():拒绝访问 mysql_select_db()拒绝访问用户" @'localhost'(使用密码:NO) PHPMyAdmin拒绝用户“root”@“localhost”的访问

顺便说一句,你可能不想再使用mysql_*函数了。新来者经常迁移到mysqli,然而这也一样乏味。相反,阅读PDO和准备好的语句。 $db =新PDO("mysql:主机=localhost;dbname=testdb", "用户名","密码");