php 检查字符串是否为空
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Checking if the string is empty
提问by bgosalci
I have a function isNotEmpty which returns true if the string is not empty and false if the string is empty. I've found out that it is not working if I pass an empty string through it.
我有一个函数 isNotEmpty 如果字符串不为空则返回 true ，如果字符串为空则返回 false 。我发现如果我通过它传递一个空字符串它不起作用。
function isNotEmpty($input)
{
$strTemp = $input;
$strTemp = trim($strTemp);
if(strTemp != '') //Also tried this "if(strlen($strTemp) > 0)"
{
return true;
}
return false;
}
The validation of the string using isNotEmpty is done:
使用 isNotEmpty 验证字符串已完成：
if(isNotEmpty($userinput['phoneNumber']))
{
//validate the phone number
}
else
{
echo "Phone number not entered<br/>";
}
If the string is empty the else doesn't execute, I don't understand why, can someone please shed some light on this please.
如果字符串为空，则 else 不执行，我不明白为什么，请有人对此有所了解。
回答by cletus
Simple problem actually. Change:
其实很简单的问题。改变：
if (strTemp != '')
to
到
if ($strTemp != '')
Arguably you may also want to change it to:
可以说，您可能还想将其更改为：
if ($strTemp !== '')
since != ''will return true if you pass is numeric 0 and a few other cases due to PHP's automatic type conversion.
因为!= ''如果您传递的是数字 0 和其他一些由于PHP 的自动类型转换的情况，则将返回 true 。
You should notuse the built-in empty()function for this; see comments and the PHP type comparison tables.
回答by Malak
PHP have a built in function called empty()the test is done by typing
if(empty($string)){...}Reference php.net : php empty
PHP 有一个称为empty()测试的内置函数，通过键入
if(empty($string)){...}Reference php.net : php empty 来完成
回答by Dexygen
I always use a regular expression for checking for an empty string, dating back to CGI/Perl days, and also with Javascript, so why not with PHP as well, e.g. (albeit untested)
我总是使用正则表达式来检查空字符串，可以追溯到 CGI/Perl 时代，也使用 Javascript，那么为什么不使用 PHP，例如（尽管未经测试）
return preg_match('/\S/', $input);
Where \S represents any non-whitespace character
\S 代表任何非空白字符
回答by Bj?rn
In your ifclause in the function, you're referring to a variable strTempthat doesn't exist. $strTempdoes exist, though.
在if函数的子句中，您指的是一个strTemp不存在的变量。$strTemp不过确实存在。
But PHP already has an empty()function available; why make your own?
但是 PHP 已经有一个empty()可用的函数了；为什么要自己做？
if (empty($str))
/* String is empty */
else
/* Not empty */
From php.net:
来自 php.net：
Return Values
Returns FALSE if var has a non-empty and non-zero value.
The following things are considered to be empty:
* "" (an empty string) * 0 (0 as an integer) * "0" (0 as a string) * NULL * FALSE * array() (an empty array) * var $var; (a variable declared, but without a value in a class)
返回值
如果 var 具有非空和非零值，则返回 FALSE。
以下内容被认为是空的：
* "" (an empty string) * 0 (0 as an integer) * "0" (0 as a string) * NULL * FALSE * array() (an empty array) * var $var; (a variable declared, but without a value in a class)
回答by troelskn
PHP evaluates an empty string to false, so you can simply use:
PHP 将空字符串评估为 false，因此您可以简单地使用：
if (trim($userinput['phoneNumber'])) {
// validate the phone number
} else {
echo "Phone number not entered<br/>";
}
回答by doctorlai
Just use strlen() function
只需使用 strlen() 函数
if (strlen($s)) {
// not empty
}
回答by svarog
I just write my own function, is_stringfor type checking and strlento check the length.
我只是编写了自己的函数，用于类型检查的is_string和用于检查长度的strlen。
function emptyStr($str) {
return is_string($str) && strlen($str) === 0;
}
print emptyStr('') ? "empty" : "not empty";
// empty
EDIT: You can also use the trimfunction to test if the string is also blank.
编辑：您还可以使用修剪功能来测试字符串是否也为空。
is_string($str) && strlen(trim($str)) === 0;
回答by TRayman
I needed to test for an empty field in PHP and used
我需要在 PHP 中测试一个空字段并使用
ctype_space($tempVariable)
which worked well for me.
这对我来说效果很好。
回答by abhishek bagul
Well here is the short method to check whether the string is empty or not.
那么这里是检查字符串是否为空的简短方法。
$input; //Assuming to be the string
if(strlen($input)==0){
return false;//if the string is empty
}
else{
return true; //if the string is not empty
}
回答by Fabian Picone
You can simply cast to bool, dont forget to handle zero.
您可以简单地强制转换为 bool，不要忘记处理零。
function isEmpty(string $string): bool {
if($string === '0') {
return false;
}
return !(bool)$string;
}
var_dump(isEmpty('')); // bool(true)
var_dump(isEmpty('foo')); // bool(false)
var_dump(isEmpty('0')); // bool(false)
