Summary of Php:empty,isset,is_null,array (0), array (), Array (""), 0, "0", "", "null", NULL

Use the following procedure to detect

$a =0;if (empty ($a)) {echo "yes|";} Else{echo "no|";} if (Isset ($a)) {echo "yes|";} Else{echo "no|";} if (Is_null ($a)) {echo "yes|";} Else{echo "no|";} if ($a) {echo "yes|";} else {echo "no|";}

So the result of a $ A difference is as follows

Summarize:

The case of empty

The value of the 1 variable is empty $var = "";

The value of the 2 variable is a string of 0 or the number 0 $var = 0; or $var = "0″

The value of the 3 variable is flase $var = flase;

4 Null is empty

5 Empty array $arr =array ();

The 6 variable only defines $var that are not assigned value;

the situation of Isset

See if a variable is already set and not empty (determine if a variable is set and are NOT NULL)

Is_null

Determine null

Judging whether it is false

The value of the 1 variable is empty $var = "";

The value of the 2 variable is a string of 0 or the number 0 $var = 0; or $var = "0″

The value of the 3 variable is flase $var = flase;

4 Null is empty

5 Empty array $arr =array ();

The 6 variable only defines $var that are not assigned value;

These whole fake

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Summary of Php:empty,isset,is_null,array (0), array (), Array (""), 0, "0", "", "null", NULL