


Introduction to PHP function to determine whether a string is empty_PHP tutorial
There are many ways to determine whether a string is empty in php, such as equal to null == null, empty, and isset can all be used to determine whether a variable or string is empty. Let me tell you about them below. introduce.
String; determine whether the string is empty; output judgment; you can modify it
The code is as follows | Copy code | ||||
if ($C_char=='') return false; //Is it empty
|
代码如下 | 复制代码 |
$str = ''; if($str==='') {//''==null ''==false ''!==false |
Example
The code is as follows | Copy code |
代码如下 | 复制代码 |
$var = 0; |
The code is as follows | Copy code |
$var = 0; // The result is true because $var is empty if (empty($var)) { echo '$var is either 0 or not set at all'; } // Result is false because $var is set if (!isset($var)) { echo '$var is not set at all'; } ?> |
On the surface, it is easy to misunderstand that the empty() function is a function that determines whether a string is empty. In fact, it is not, and I suffered a lot because of it.
The empty() function is used to test whether the variable has been configured. If the variable already exists, is a non-empty string, or is non-zero, a false value is returned; otherwise
true value. Therefore, when the value of the string is 0, true is also returned, which is to execute the statement inside empty. This is the trap.
For example: Assume $value = 0; then empty($value)=false.
To determine whether a string is empty, you can determine it like this: if ($value=="") ...
* Format: bool empty (mixed var)
* Function: Check whether a variable is empty
* Return value:
* If the variable does not exist, return TRUE
* If the variable exists and its value is "", 0, "0", NULL,, FALSE, array(), var $var; and an object without any attributes, return
TURE
* If the variable exists and the value is not "", 0, "0", NULL,, FALSE, array(), var $var; and an object without any attributes, return
FALSE
isset() and empty() judgment methods:
The code is as follows
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echo " isset test:
" ;
' ; }
" ;
' ; } else { echo 'Variable $var does not exist!
' ; } http://www.bkjia.com/PHPjc/628864.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/628864.htmlTechArticleThere are many ways to determine whether a string is empty in php, such as equal to empty == null, empty, isset can be used to determine whether a variable or string is empty. Let me share it with you...

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