PHP use Empty () function to note _php tutorial

When you use empty () to determine the number 0, empty () will also return true, that is, if your variable may appear the number 0 this variable, to use Isset () to judge it will be better!!

On the face of it, it is easy to misunderstand that the empty () function is a function that determines whether a string is empty, in fact it is not, I eat a lot of losses.

The empty () function is used to test whether a variable has been configured. Returns False if the variable already exists, a non-empty string, or nonzero, and returns a true value. So, when the value of the string is 0 o'clock, it also returns True, which is the statement inside the empty. This is the trap.

The code is as follows	Copy Code
$a =array ("1" = "DDF"); Var_dump (Empty ($a));///boolean false $b = 0; Var_dump (Empty ($b)); Boolean true

Advise everyone, be careful to use the empty () function.

Judging if the string is empty, you can say so: if ($value = = "") ...
* Format: BOOL empty (mixed Var)
* Function: Check if a variable is empty
* Return value:
* Returns TRUE if the variable does not exist
* If the variable exists and its value is "", 0, "0", NULL, FALSE, Array (), Var $var; and objects that do not have any properties, the TURE is returned.
* If the variable exists and the value is not "", 0, "0", NULL, FALSE, Array (), Var $var; And an object that does not have any properties, it returns FALSE
* Version: PHP 3, PHP 4, PHP 5

On the face of it, it is easy to misunderstand that the empty () function is a function that determines whether a string is empty, in fact it is not, I eat a lot of losses. The empty () function is used to test whether a variable has been configured. Returns False if the variable already exists, a non-empty string, or nonzero, and returns a true value. So, when the value of the string is 0 o'clock, it also returns True, which is the statement inside the empty. This is the trap. such as: suppose $value = 0; Then empty ($value) =false. Advise everyone, be careful to use the empty () function. Judging if the string is empty, you can say so: if ($value = = "") ... Format: bool Empty (mixed Var) function: Checks whether a variable is a null return value: Returns TRUE if the variable does not exist if the variable exists and its value is "", 0, "0", NULL, FALSE, Array (), Var $var; and objects that do not have any properties, return TURE if the variable exists and the value is not "", 0, "0", NULL, FALSE, Array (), Var $var; and an object without any attributes, it returns FALSE version: Php 3, PHP 4, PHP 5

When you use empty to check the results returned by a function, you get an error: Fatal Error:can ' t uses function return value in write context

For example:

The code is as follows	Copy Code
echo Empty (strlen (' be-evil.org '));

To the PHP manual, where the empty function describes the following text:

Note:empty () Only checks variables as anything else would result in a parse error. In other words, the following would not Work:empty (trim ($name)).

Empty () detects only variables and detects anything that is non-variable will result in parsing errors!

Therefore, we cannot take empty to directly detect the value returned by the function, the solution of the above example is as follows:

The code is as follows	Copy Code
$length = strlen (' be-evil.org '); echo Empty ($length); ?>

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