PHP judgment string for null function introduction _php tutorial

In PHP, there are a number of methods to judge the string is empty, such as equal to the empty = = Null,empty,isset can be used to determine whether a variable or string is empty oh, I would like to give you friends to introduce.

string; Determines whether the string is empty; You can do it in a little bit.

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if (Empty ($C _char)) return false; Whether it has been set if ($C _char== ") return false; is empty

Use = = ""

Cases

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$str = "; if ($str = = = ") {//' ==null ' ==false '!==false Echo ' str is a NULL string. '; } ?>

Empty to determine if NULL

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$var = 0; The result is true because the $var is empty if (empty ($var)) { Echo ' $var is either 0 or isn't set at all '; } The result is false because the $var has been set if (!isset ($var)) { Echo ' $var is not set at all '; } ?>

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 a value of False if the variable already exists, a non-empty string, or nonzero;

A value of true. 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.

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 return

TURE
* If the variable exists and the value is not "", 0, "0", NULL, FALSE, Array (), Var $var; and objects that do not have any properties, the return

FALSE

Isset () and empty () determine the method:

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Function Demo () { $var = _post[' A '];//takes over the parameters echo "Isset test: " ; if (Isset ($var)) n { Echo ' Variable $var exists! ' ; }else { echo ' variable $var does not exist! ' ; } echo "Empty test: " ; if (empty ($var)) { The value of ECHO ' variable $var is null ' ; } Else { echo ' variable $var value is not empty ' ; } echo "Variable direct test: " ; if ($var) { Echo ' Variable $var exists! ' ; } else { echo ' variable $var does not exist! ' ; }

http://www.bkjia.com/PHPjc/628864.html www.bkjia.com true http://www.bkjia.com/PHPjc/628864.html techarticle in PHP, there are a number of ways to judge the string is empty, like equal to empty = = Null,empty,isset can be used to determine whether a variable or string is empty oh, let me give you friends to divide ...

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